[avalanche] Extract the compact proofs functional test to its own file

Summary:
This is not really related to the proof inventories, and more tests are coming so better split it out. There is no change in behavior.

Depends on D11388.

Test Plan:

ninja check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D11533