[avalanche] pass a fRelayProofs flag to the Peer struct
Summary:
This moves the responsibility of knowing whether avalanche is enabled to a scope that knows of the processor pointer. In a next diff, we will use the processor pointer to determine whether avalanche is enabled.
Depends on D16311
Test Plan: ninja all check-all
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D16312