draft impl for EIP-7805's p2p interface and inclusion list pool.

[h3lio5]

This PR proposes the following changes:

• create a new inclusion list pool
• impl of p2p interface: gossip validation, subnet
• signature utils

[github-actions]

Unit Test Results

       12 files   -        3    2 104 suites   - 526   1h 1m 54s ⏱️ - 16m 49s
  5 796 tests  -    576    5 739 ✔️  -    131    57 💤  - 445  0 ❌ ±0 
35 428 runs   - 8 853  35 200 ✔️  - 8 403  228 💤  - 450  0 ❌ ±0 

Results for commit 1b7293b. ± Comparison against base commit f996d18.

♻️ This comment has been updated with latest results.

[tersec]

/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(50, 59) Error: undeclared field: 'seconds' for type system.uint64 [type declared in /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nimbus-build-system/vendor/Nim/lib/system/basic_types.nim(12, 3)]
make: *** [Makefile:441: nimbus_beacon_node] Error 1

[tersec]

https://github.com/status-im/nimbus-eth2/actions/runs/16248920772/job/45876335181?pr=7290 (the linux-amd64 target, though it's representative here):

2025-07-13T12:34:24.5405193Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/digest.nim(35, 9) Hint: BLST SHA256 backend enabled [User]
2025-07-13T12:34:24.5412603Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/digest.nim(49, 9) Hint: Hashtree SHA256 backend enabled [User]
2025-07-13T12:34:27.1689107Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(19, 8) Warning: imported and not used: 'sequtils' [UnusedImport]
2025-07-13T12:34:27.1692347Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(19, 18) Warning: imported and not used: 'typetraits' [UnusedImport]
2025-07-13T12:34:27.1696384Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(31, 10) Warning: imported and not used: 'byteutils' [UnusedImport]
2025-07-13T12:34:27.1699691Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(30, 10) Warning: imported and not used: 'bitops2' [UnusedImport]
2025-07-13T12:34:27.1702857Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(29, 9) Warning: imported and not used: 'strutils' [UnusedImport]
2025-07-13T12:34:27.1706179Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(21, 3) Warning: imported and not used: 'chronicles' [UnusedImport]
2025-07-13T12:34:28.1881270Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/signatures.nim(435, 23) template/generic instantiation of `compute_signing_root` from here
2025-07-13T12:34:28.1884476Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/helpers.nim(182, 32) template/generic instantiation of `hash_tree_root` from here
2025-07-13T12:34:28.1887637Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(747, 20) template/generic instantiation of `merkleizeFields` from here
2025-07-13T12:34:28.1890949Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(748, 8) template/generic instantiation of `enumerateSubFields` from here
...
2025-07-13T12:34:38.6626744Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/signatures.nim(435, 23) template/generic instantiation of `compute_signing_root` from here
2025-07-13T12:34:38.6629019Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/helpers.nim(182, 32) template/generic instantiation of `hash_tree_root` from here
2025-07-13T12:34:38.6631426Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(747, 20) template/generic instantiation of `merkleizeFields` from here
2025-07-13T12:34:38.6634151Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(748, 8) template/generic instantiation of `enumerateSubFields` from here
2025-07-13T12:34:38.6636844Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(498, 17) template/generic instantiation of `addChunkDirect` from here
2025-07-13T12:34:38.6639489Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(499, 27) template/generic instantiation of `hash_tree_root` from here
2025-07-13T12:34:38.6643098Z /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(1243, 21) Error: Limited types should not be used with SSZ (ABI differences); usage of 'toSszType' is an {.error.} defined at /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/base.nim(636, 15)
2025-07-13T12:34:38.7125505Z make: *** [Makefile:441: validator_db_aggregator] Error 1

There are two parts here, repeated several times across different build targets:

/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(19, 8) Warning: imported and not used: 'sequtils' [UnusedImport]
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(19, 18) Warning: imported and not used: 'typetraits' [UnusedImport]
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(31, 10) Warning: imported and not used: 'byteutils' [UnusedImport]
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(30, 10) Warning: imported and not used: 'bitops2' [UnusedImport]
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(29, 9) Warning: imported and not used: 'strutils' [UnusedImport]
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/focil.nim(21, 3) Warning: imported and not used: 'chronicles' [UnusedImport]

These should just not be imported, if they're not used. In current unstable (trunk) branch, this has been turned into a compilation error, not only warning.

The other part is:

/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/signatures.nim(435, 23) template/generic instantiation of `compute_signing_root` from here
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/helpers.nim(182, 32) template/generic instantiation of `hash_tree_root` from here
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(747, 20) template/generic instantiation of `merkleizeFields` from here
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(748, 8) template/generic instantiation of `enumerateSubFields` from here
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(498, 17) template/generic instantiation of `addChunkDirect` from here
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(499, 27) template/generic instantiation of `hash_tree_root` from here
/github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-ssz-serialization/ssz_serialization/merkleization.nim(1243, 21) Error: Limited types should not be used with SSZ (ABI differences); usage of 'toSszType' is an {.error.} defined at /github-runner/github-runner-node-01/workspace/nimbus-eth2/nimbus-eth2/beacon_chain/spec/datatypes/base.nim(636, 15)

which is from the compute_signing_root(message, domain) call in:

# https://github.com/ethereum/consensus-specs/blob/dev/specs/_features/eip7805/validator.md#constructing-a-signed-inclusion-list
func compute_inclusion_list_signing_root*(
    fork: Fork, genesis_validators_root: Eth2Digest,
    message: InclusionList): Eth2Digest =
  let domain = get_domain(
    fork, DOMAIN_INCLUSION_LIST_COMMITTEE, message.slot.epoch(),
    genesis_validators_root)
  compute_signing_root(message, domain) 

where InclusionList is defined as

type
  # https://github.com/ethereum/consensus-specs/blob/v1.6.0-alpha.2/specs/_features/eip7805/beacon-chain.md#inclusionlist
  InclusionList* = object
    slot*: Slot
    validator_index*: ValidatorIndex
    inclusion_list_committee_root: Eth2Digest
    transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]
    inclusion_list_committee_root*: Eth2Digest
    transactions*: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]

it's likely complaining about ValidatorIndex here, and ValidatorIndex for SSZ purposes is a uint64. There's an internal representation of ValidatorIndex which differs, but that can't be used at the SSZ boundary as here. So probably the relevant line has to be

    validator_index*: uint64

with any relevant conversions to/from ValidatorIndex (which is not, in fact, a uint64) handled internally.

[h3lio5]

Thanks for the quick and detailed help with debugging! And sorry for my delayed response-- I was waiting to fix all the build errors before pushing the code.