Revert recent coin selection changes

Summary:
Revert D7674 and D7691 (since it built on top of the prior).

D7674 is failing all sanitizer builds and appears to be adding flakiness
to ninja check in some configurations. There's hints that backporting up
to PR17261 may fix one or more of these problems. Until then, we should
revert as it's making diff tests unreliable and incredibly noisy, as
well as zero reliability on sanitizer builds.

I opted to revert them together as one patch in order to give us the
option of un-reverting them both as a single change (by reverting this
change).

This reverts commit 78322dfdfa3c31b410b227fcde1d611d6f6cb9d8 and 28efd9a54daa873afb4512911bcc8bb31b5cbda9

Test Plan:

ninja all check check-functional

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D7729