[net_processing] Move ProcessMessage to PeerLogicValidation

Summary:
Completes backport (2/2) of core PR19704.

Depends on D8781.

Test Plan:

ninja all check-all

ninja bitcoin-fuzzers

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D8782