Backport all changes related to checkqueue.h and its test from Core

Summary: As per title. Backporting one by one did not seems realitic on that one.

Test Plan:

make check

Reviewers: #bitcoin_abc, schancel

Reviewed By: #bitcoin_abc, schancel

Subscribers: schancel, teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1771