Implement Branch and Bound coin selection in a new file
Create a new file for coin selection logic and implement the BnB algorithm in it.
This is a partial backport of Core PR10637 : https://github.com/bitcoin/bitcoin/pull/10637/commits/0185939be6f7c5554b864e33657ce610fd434e18
Unfortunately, the test has way more dependencies, so it'll have to come separately.
Depends on D3248
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D3249