Merge #17925: Improve UpdateTransactionsFromBlock with Epochs

bd5a02692853f7240a4fdc593d7d0123d7916e45 Make UpdateTransactionsFromBlock use Epochs (Jeremy Rubin)
2ccb7cca4ac67198ac89bd58f5b4ae41a5163ceb Add Epoch Guards to CTXMemPoolEntry and CTxMemPool (Jeremy Rubin)

Pull request description:

  UpdateTransactionsFromBlock is called during a re-org. When a re-org occurs, all of the transactions in the mempool may be descendants from a transaction which is in the pre-reorg block. This can cause us to propagate updates, worst case, to every transaction in the mempool.

  Because we construct a `setEntries setChildren`, which is backed by a `std::set`, it is possible that this algorithm is `O(N log N)`.

  By using an Epoch visitor pattern, we can limit this to `O(N)` worst case behavior.

  Epochs are also less resource intensive than almost any set option (e.g., hash set) because they are allocation free.

  This PR is related to https://github.com/bitcoin/bitcoin/pull/17268, it is a small subset of the changes which have been refactored slightly to ease review. If this PR gets review & merge, I will follow up with more PRs (similar to #17268) to improve the mempool

ACKs for top commit:
  sdaftuar:
    ACK bd5a02692853f7240a4fdc593d7d0123d7916e45
  adamjonas:
    Just to summarize for those looking to review - as of bd5a026 there are 3 ACKs (@sdaftuar, @ariard, and @hebasto) and one "looks good" from @ajtowns with no NACKs or any show-stopping concerns raised.
  ajtowns:
    ACK bd5a02692853f7240a4fdc593d7d0123d7916e45 (code review)
  ariard:
    Code review ACK bd5a026
  hebasto:
    ACK bd5a02692853f7240a4fdc593d7d0123d7916e45, modulo some nits and a typo.

Tree-SHA512: f0d2291085019ffb4e1119edeb9f4a89c1a572d1cb5b4bdf5743dd0152e721e1935f5155dcae84e1e5bda5ffdf6224c488c1e200bd33bedca9f5ca22d5f5139f

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