[backport#17304 16/18] Refactor: Move RewriteDB code out of CWallet

Summary:
This commit does not change behavior.

https://github.com/bitcoin/bitcoin/pull/17304/commits/089e17d45c8147bd0303bcbf02dc0f7d6b387f2a

Depends on D7162

Partial backport of Core PR17304

Test Plan:

ninja check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7163