Multiple state sync commitments per epoch

[goran-ethernal]

Description

Implemented multiple commitments per epoch feature, as per RFC-178. Wrote appropriate UTs, and a e2e test (TestE2E_Bridge_MultipleCommitmentsPerEpoch).

Process of building commitments is as follows:

1. Using the event tracker, listen for state sync events, and store them in db.
2. At the beginning of an epoch, check if we have enough events to build a commitment (minimum size of commitment at least, which is 2 events).
   a. If we have, build a commitment, sign it, and gossip a vote.
   b. If we do not have enough state sync events, wait until we have enough.
3. If we gossiped a commitment which did not have a full size (10 events), on every state sync event that was received in the meantime, create a new commitment (with number of events of the old gossiped commitment, plus the new state syncs), sign it and gossip it.
4. At every sprint block, check which of the gossiped commitments have quorum of votes, find the largest commitment that has quorum, and submit it.
5. Once the block is finalized, check it to see if any was submit commitment transaction occurred.
   a. If there is, create a merkle tree, build state sync proofs, and save them to boltDb. Also, discard any cached commitment,
   since a new one will be built in the next block.
   b. If there isn’t, wait until some proposer submits the largest commitment with quorum.
6. Once the epoch ends, and a new epoch is started, discard any pending commitments (that were built in the previous epoch, and are waiting for quorum of messages), since the validator set changes (we need to rebuild the last pending checkpoint in the new epoch).

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• I have tested this code with the official test suite
• I have tested this code manually

[codecov]

Codecov Report

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[Stefan-Ethernal]

Generally looks good, but leaving a couple of comments to consider.

[Stefan-Ethernal]

Generally looks good, but leaving a couple of comments to consider.

[ferranbt]

Some general comments.

[Stefan-Ethernal]

LGTM