qa: Move wait_until to util

Summary:
Backport core's PR11068

Depends on D1063 and D1064

Test Plan:

make check
./test/functional/test_runner.py --extended

Reviewers: #bitcoin_abc, schancel, deadalnix

Reviewed By: #bitcoin_abc, schancel

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1065