Add extra logging of asmap use and bucketing

Summary:
Completes backport 4/4 of core PR16702:
https://github.com/bitcoin/bitcoin/pull/16702/commits/3c1bc40205a3fcab606e70b0e3c13d68b2860e34

Depends on D8196.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D8197