Use mockable time for peer connection time

Summary:
This allows to revert the temporary fix in test test/functional/p2p_timeouts.py (see 10965)

This is a backport of core#23758 [2/3]
https://github.com/bitcoin/bitcoin/pull/23758/commits/fa663a4c0d20487ed3f7a93e1c2ca9932b05f5a8

Depends on D11084

Note: due to out of sequence backports, we do not yet have void SetMockTime(std::chrono::seconds mock_time_in), so I used void SetMockTime(int64_t nMockTimeIn) instead.

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11085