validation: add CChainState.m_from_snapshot_blockhash
This parameter is unused, but in future commits will allow ChainstateManager to differentiate between chainstates created from a UTXO snapshot from those that weren't.
Partial backport (1/5) of core PR17737:
ninja all check-all
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D8537