Create an Ethereum bridge sub-crate

…llocator

Plug `BlockSpaceAllocator` logic into `ProcessProposal`

Malformed transactions can cause the node to panic because this
function unwraps values. Return the proper error, or a failure if asked
to verify a transaction with no shielded part.

* ray/vp-verify-masp-failure:
  changelog: add #942
  vp_verify_masp: avoid panicking unwrap()s

Merge v0.12.1

Fix Tendermint release in CI

…lock-proposal

…tor-specs

Write specs for the `BlockSpaceAllocator`

…posal

Optimize block proposal

…ht offs

…al-alloc

Fix allocator logic in `ProcessProposal`