EPIC: Implement and integrate CometMock

[p-offtermatt]

Problem

We would like to mock out CometBFT in our end-to-end tests, since we
want to test the underlying application, but we do not care about actually running
a replicated state machine resistant to byzantine faults - just running a state machine is enough for testing.
Mocking out the consensus layer means we can skip
waiting for the network communication in the potentially multiple rounds
needed for CometBFT to come to consensus.
Thus, this can make the existing tests which are running full nodes faster.

Looking further, it can also enable writing tests with new functionality,
as CometMock can mock arbitrary timestamps coming from Comet,
and we can finely control which validators sign and don't sign which blocks.

Closing criteria

CometMock has been implemented in a proper repository.
It is integrated in our CI pipeline(s) and covers all common usecases
in a way that is delightful to use.

Problem details

Task list

Must have

Beta Give feedback

1. Integrate basic CometMock functionality in the e2e tests #935
   scope: testing +1
   
2. Implement CometMock-specific functionality: Advancing Blocks, Advancing Time, and Downtime #938
   scope: testing +1
   
3. Add CometMock specific functionality: Advancing Time, Downtime & Advancing Blocks #1006
   +0
   
4. Add CometMock specific functionality: Light Client Attacks #1248
   S: Productivity +1
   
5. Enable CometMock in e2e tests #1182
   +0
   

Nice to have

Beta Give feedback

1. CometMock: Add robust arg parsing #937
   +0
   
2. CometMock: Add reconnect and crash recovery support to CometMock #936
   S: Productivity scope: testing +2