p2p, rpc, test: address rate-limiting follow-ups

Summary:
Incorporates review feedback in core#22387

This is a backport of core#22604
Depends on D10941

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10942