test: feature_init, ensure indexes are synced prior to perturbing files
Summary:
This concludes backport of core#32835
https://github.com/bitcoin/bitcoin/pull/32835/commits/4207d9bf823bea9f94b484ebf3c9274ca781b245
Depends on D18625
Test Plan: ninja check-functional
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D18626