validation: Pass in chain to ::TestLockPointValidity

Summary:
This is a backport of core#20750 [14/17]
https://github.com/bitcoin/bitcoin/pull/20750/commits/71734c65dc491a4bb654ccbb7a1dd0e12131cee4

Depends on D11196

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11201