[backport#16208 2/2] Restrict lifetime of ReserveDestination to CWallet::CreateTransaction

Summary:
https://github.com/bitcoin/bitcoin/pull/16208/commits/e10e1e8db043e9b7c113e07faf408f337c1b732d

Depends on D6800

Concludes backport of Core PR16028

Test Plan:

ninja check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D6802