Add a method to make addrman deterministic

Summary: This is actually done in tests by subclassing CAddrMan, but making it part of the main CAddrMan class makes it possible to use a deterministic address manager as a member of CConnman. There is no change in behavior.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Subscribers: sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D11827