Move original knapsack solver tests to coinselector_tests.cpp

Summary:
This is a partial backport of Core PR10637 : https://github.com/bitcoin/bitcoin/pull/10637/commits/cd927ff3283fc23a5f42c178e10bcaf5409bb7ea

Depends on D3252 and D3289

Test Plan:

make check

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D3290