Add additional checks to consensus contracts

[guidanoli]

This PR adds the following checks to Authority and Quorum:

• lastProcessedBlockNumber < block.number: validators cannot process blocks in the future
• lastProcessedBlockNumber % epochLength == (epochLength - 1): validators have to validate blocks until the last block of an epoch
• there cannot be two accepted claims for the same epoch

The last point is implemented differently for Authority and Quorum:

• Authority stores the set of epochs for which a claim was accepted.
• Quorum stores the set of validators that have submitted a claim for a given epoch.

Both contracts use OpenZeppelin's bitmap data structure to store sets.
In Authority, epochs are identified by their number (lastProcessedBlockNumber / epochLength)
In Quorum, validators are identified by their ID.
Because of how OpenZepplein implements bitmaps and how these numbers are close to one another, this saves gas because fewer storage slots have to be read/written.

Other notable things about this PR:

• We've bumped solc from 0.8.23 to 0.8.29 (to use require(bool, CustomError) syntax)
• Adds custom errors to IConsensus for each of these checks
• In the case of Quorum, if a validator submits the same claim twice, it is simply ignored, and no error is reverted (idempotence). This behavior/feature is a consequence of implementation details.
• Added two new view functions to IQuorum to consult information about validators that have submitted any claim for a particular epoch (basically exposing the newly-added state variables through the interface).
• Added tests to cover all cases