[refactor] Move ComputeBlockVersion into VersionBitsCache

Summary:
This also changes ComputeBlockVersion to take the versionbits cache mutex once, rather than once for each versionbits deployment.

This concludes backport of core#19438
https://github.com/bitcoin/bitcoin/pull/19438/commits/4a69b4dbe0d7f504811b67c399da7e6d11e4f805
https://github.com/bitcoin/bitcoin/pull/19438/commits/c5f36725e877d8eb492383844f8ef7535466b366
https://github.com/bitcoin/bitcoin/pull/19438/commits/e48826ad87b4f92261f7433e84f48dac9bd9e5c3

Depends on D12225

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12226