Upgrade to CometBFT 0.38

[aakoshh]

Informal Systems attempt to maintain the version of the spec on release branches that correlates to that specific release series:

• ABCI v0.17 is in the v0.34.x series here: https://github.com/cometbft/cometbft/tree/v0.34.x/spec/abci
• ABCI v1.0, with PrepareProposal and ProcessProposal, is in the v0.37.x series here: https://github.com/cometbft/cometbft/tree/v0.37.x/spec/abci
• ABCI v2.0, with vote extensions and FinalizeBlock, is in the v0.38.x series here: https://github.com/cometbft/cometbft/tree/v0.38.x/spec/abci

The v0.38 docs are currently being rendered, but are not publicly linked to via the dropdown menu because we're still in RC at the moment: https://docs.cometbft.com/v0.38/spec/abci/

FinalizeBlock can be interesting for parallel execution, which IIUC the FVM now supports somehow.

[raulk]

parallel execution, which IIUC the FVM now supports somehow.

The FVM doesn't support parallel execution yet, but it's in the future roadmap for sure.

[raulk]

See the v0.38.0 CHANGELOG for more info: https://github.com/cometbft/cometbft/blob/v0.38.0/CHANGELOG.md#v0380

Action items

• Investigate new vote extension ABCI methods -- when are they called by the consensus engine, what is the impact of not implementing them, and/or must we implement them?
• Coalesce the block execution methods into FinalizeBlock.
• Provide a clean upgrade path for adopters.

[raulk]

@ec2 is experimenting here: https://filecoinproject.slack.com/archives/C04JR5R1UL8/p1716399543175629