Change time variable type to std::chrono::seconds in src/net_processing.cpp

Summary:
This changes some of the remaining time variable in net_processing.cpp from int64_t to std::chrono. The PR description claims to change all the remaining variables in net_processing, but more are done in follow-up PR 23832

This is a backport of core#23801

It also includes commit https://github.com/bitcoin/bitcoin/pull/21562/commits/a28bfd1d4cfa523a6abf3832dbfd6183cd546944

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D13374