consensus: Start from saved iteration on restart

[fed-franz]

Implements #1908

• move the committee generation code from phase run function to the new generate_committee in IterationCtx
• move get_sortition_config to IterationCtx
• remove save_committee
• if starting from saved_iteration != 0, generate all committees from iteration 0 to saved_iteration before running the step loop. This is needed in order to ensure we don't panic due to a missing committee when processing a message from a past iteration¹.
• extract next generator on Validation/Ratification step instead of Proposal
• fix 'iteration < CONSENSUS_MAX_ITER' bug: last iteration is actually CONSENSUS_MAX_ITER-1, so when iteration = CONSENSUS_MAX_ITER-1 we should NOT extract the next generator

Footnotes

1. This is a naive approach just to be on the safe side and not waste too much time. A future refactor should actually allow creating a committee on the fly, as needed (if we receive a message from the past and we don't have the committee, than generate it). ↩

[herr-seppia]

LGTM

[fed-franz]

Tested Successfully:

{"timestamp":"2024-09-06T16:53:17.612069Z","level":"DEBUG","event":"init","name":"sel","round":18,"iter":0,"target":"dusk_consensus::proposal::step"}
{"timestamp":"2024-09-06T16:53:24.630874Z","level":"DEBUG","event":"init","name":"validation","round":18,"iter":0,"hash":"7e3f3e72f5a0ac69...e8c557aaaf46704b","target":"dusk_consensus::validation::step"}
{"timestamp":"2024-09-06T16:53:25.291213Z","level":"DEBUG","event":"init","name":"ratification","round":18,"iter":0,"vote":"Vote: Valid(7e3f3e72f5a0ac69...e8c557aaaf46704b)","fsv_bitset":102064123,"quorum_type":"Valid","target":"dusk_consensus::ratification::step"}


{"timestamp":"2024-09-06T16:53:38.218518Z","level":"INFO","event":"VM accepted state loaded","state_root":"8ad73ffe48cecdbd3984578ddb31db83a8132a8a397b83b32feb19e4e62f94d7","target":"node::chain::acceptor"}
{"timestamp":"2024-09-06T16:53:38.226778Z","level":"DEBUG","event":"restored iteration","ru.round":18,"iter":1,"target":"dusk_consensus::consensus"}
{"timestamp":"2024-09-06T16:53:38.227156Z","level":"DEBUG","event":"init","name":"sel","round":18,"iter":1,"target":"dusk_consensus::proposal::step"}
{"timestamp":"2024-09-06T16:53:38.831083Z","level":"INFO","event":"block accepted","height":18,"iter":0,"hash":"7e3f3e72f5a0ac69...e8c557aaaf46704b","txs":0,"state_hash":"860c9b4f6b8ab66c...056f5ea97f59791e","fsv_bitset":102080507,"ssv_bitset":55187455,"block_time":10,"generator":"nvdsjA8biVgXQc7f","dur_ms":"78","label":"Attested(1)","target":"node::chain::acceptor"}

[herr-seppia]

LGTM