[backport#16443 3/3] Cover UTXO set access with lock annotations

Summary:
i.e. any CoinsViews members. Adds a lock acquisition to gettxoutsetinfo RPC
to comply with added annotations.

Co-authored-by: Russell Yanofsky <russ@yanofsky.org>

https://github.com/bitcoin/bitcoin/pull/16443/commits/582d2cd74754d6b9a2394616a9c82a89d2d71976

Depends on D7581

Concludes backport of Core PR16443

Test Plan:

cmake .. -DENABLE_SANITIZERS=address
ninja check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7582