net: Make addr relay mockable, add test
As usual: Switch to std::chrono time to be type-safe and mockable Add basic test that relies on mocktime to add code coverage
Backport of core PR18454.
ninja all check-all
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D8479