validation: Farewell, global Chainstate!

Summary:
This concludes backport of core#21866 [12/12]
https://github.com/bitcoin/bitcoin/pull/21866/commits/6f994882deafe62e97f0a889d8bdb8c96dcf913d

Depends on D11752

Backport note: the changes in qt/test/apptests.cpp are done in a different commit in the source material, but this is incorrect and belongs here (as explained in D11752)

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11753