node/chainstate: Decouple from ShutdownRequested

Summary:

...instead allow optionally passing in a std::function<bool()>

Partial backport of core#23280:
https://github.com/bitcoin/bitcoin/pull/23280/commits/4da9c076d1cf12728730bb1f7e8906d4e9bfaba5

Depends on D12577.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D12578