[backport#16237 2/3] Replace CReserveKey with ReserveDestinatoin

Summary:
Instead of reserving keys, reserve destinations which are backed by keys

https://github.com/bitcoin/bitcoin/pull/16237/commits/33d13edd2bda0af90660e275ea4fa96ca9896f2a

Depends on D6716

Partial backport of Core PR16237

Test Plan:

ninja check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6717