validation: Pass in chainstate to ::PruneBlockFilesManual

Summary:
This is a backport of core#21055 [5/16]
https://github.com/bitcoin/bitcoin/pull/21055/commits/63e4c7316a537900f525e221d8042587b443cc3d

Depends on D11209

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11210