Add basic test for bitcoin-wallet salvage

Summary:
Partial backport (2/11) of core PR18918:
https://github.com/bitcoin/bitcoin/pull/18918/commits/cdd955e580dff99f3fa440494ed2b348f7f094af

Depends on D8588.

Test Plan:

ninja check-functional

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8589