[avalanche] Add an avaproof network permission for bypassing the inv tracking limit

Summary:
This flag is unset by default and bypasses the proof inventory tracking
limit so an unlimited number of proofs can be downloaded from a peer.
The flag bit is set at the latest position to prevent from futur
conflicts.

Part of T1611.

Test Plan:

ninja all check-all
ninja fuzz-net_permissions

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Maniphest Tasks: T1611

Differential Revision: https://reviews.bitcoinabc.org/D9608