[avalanche] Poll for unorphaned proofs

Summary:
When a proof that sits in the orphan pool becomes valid, it needs to be voted on just like any new proof received from the network.

Depends on D11672 and D11676.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D11677