[avalanche] Run the proofs cleanup on a schedule

Summary: This diffs runs the dangling proofs cleanup every 5 minutes and add tests for it.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Subscribers: sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D11667