* Store quorumHash of first mined commitment in evoDb
This allows to skip scanning for quorums below this block.
* Speed up CQuorumManager::ScanQuorums
This does 2 things:
1. Only call HasQuorum for blocks that are potentially a quorumBlockHash
These are only blocks which are at index 0 of each DKG interval
2. Stop scanning for quorums when we get below the first block that
contained a commitment. If no commitment was ever mined, we bail out
immediately.
* Return result instead of {}
* Remove HasQuorum() call as GetQuorum already does this
* Remove unnecessary "if (!qc.IsNull()))"
It's already checked at the top of the loop
* When necessary, remove DB_FIRST_MINED_COMMITMENT from evoDb in UndoBlock
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