MOVEONLY: update_lock_points to txmempool.h

Summary:
This concludes backport of core#23683
https://github.com/bitcoin/bitcoin/pull/23683/commits/b6002b07a36f0d58dc6becd04bfcf78599056b7c

Depends on D12453

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12454