130728: kvserver: add rac2 v1 integration tests r=sumeerbhola a=kvoli

1st commit from #130619.
2nd-3rd commits from #131106.
4th-5th commits from #131107.
6th-7th commits from #131108.
8th commit from #131109.

---
Introduce several tests in `flow_control_integration_test.go`, mirroring
the existing tests but applied to the replication flow control v2
machinery.

The tests largely follow an identical pattern to the existing v1 tests,
swapping in rac2 metrics and vtables.

The following tests are added:

```
TestFlowControlBasicV2
TestFlowControlRangeSplitMergeV2
TestFlowControlBlockedAdmissionV2
TestFlowControlAdmissionPostSplitMergeV2
TestFlowControlCrashedNodeV2
TestFlowControlRaftSnapshotV2
TestFlowControlRaftMembershipV2
TestFlowControlRaftMembershipRemoveSelfV2
TestFlowControlClassPrioritizationV2
TestFlowControlQuiescedRangeV2
TestFlowControlUnquiescedRangeV2
TestFlowControlTransferLeaseV2
TestFlowControlLeaderNotLeaseholderV2
TestFlowControlGranterAdmitOneByOneV2
```

These tests all have at least two variants:

```
V2EnabledWhenLeaderV1Encoding
V2EnabledWhenLeaderV2Encoding
```

When `V2EnabledWhenLeaderV1Encoding` is run, the tests use a different
testdata file, which has a `_v1_encoding` suffix. A separate file is
necessary because when the protocol enablement level is
`V2EnabledWhenLeaderV1Encoding`, all entries which are subject to
admission control are encoded as `raftpb.LowPri`, regardless of their
original priority, as we don't want to pay the cost to deserialize the
raft admission meta.

The v1 encoding variants retain the same comments as the v2 encoding,
however any comments referring to regular tokens should be interpreted
as elastic tokens instead, due to the above.

Two v1 tests are not ported over to v2:

```
TestFlowControlRaftTransportBreak
TestFlowControlRaftTransportCulled
```

These omitted tests behave identically to `TestFlowControlCrashedNodeV2`
as rac2 is less tightly coupled to the raft transport, instead operating
on replication states (e.g., `StateProbe`, `StateReplicate`).

--- 

Add `TestFlowControlV1ToV2Transition`, which ratchets up the enabled
version of replication flow control v2:

```
v1 protocol with v1 encoding =>
v2 protocol with v1 encoding =>
v2 protocol with v2 encoding
```

The test is structured to issue writes and wait for returned tokens
whenever the protocol transitions from v1 to v2, or a leader changes.

More specifically, the test takes the following steps:

```
(1) Start n1, n2, n3 with v1 protocol and v1 encoding.
(2) Upgrade n1 to v2 protocol with v1 encoding.
(3) Transfer the range lease to n2.
(4) Upgrade n2 to v2 protocol with v1 encoding.
(5) Upgrade n3 to v2 protocol with v1 encoding.
(6) Upgrade n1 to v2 protocol with v2 encoding.
(7) Transfer the range lease to n1.
(8) Upgrade n2,n3 to v2 protocol with v2 encoding.
(9) Transfer the range lease to n3.
```

Between each step, we issue writes, (un)block admission and observe the
flow control metrics and vtables.

Resolves: #130431
Resolves: #129276
Release note: None

131252: roachtest: port decommission/mixed-versions r=srosenberg,DarrylWong a=renatolabs

This commit ports the `decommission/mixed-versions` roachtest to use the `mixedversion` framework (instead of the old `newUpgradeTest` API). It also updates `acceptance/decommission-self` since both tests used shared functionality that needed to be updated. Prior to this commit, the acceptance test used the old upgrade test API even though it was not an upgrade test.

Fixes: #110531
Fixes: #110530

Release note: None

131364: upgrades: give test an additional core under remote exec r=rail a=rickystewart

This has been timing out.

Epic: none
Release note: None

Co-authored-by: Austen McClernon <[email protected]>
Co-authored-by: Renato Costa <[email protected]>
Co-authored-by: Ricky Stewart <[email protected]>