wallet: Switch to using output groups instead of coins in coin selection

Summary:
This is a partial backport of Core PR12257 : https://github.com/bitcoin/bitcoin/pull/12257/commits/59d6f7b4e2f847ec1f2ff46c84e6157655984f85

Depends on D3377, D3389, D3392, D3387 and D3393

Test Plan:

make check

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D3394