[avalanche] Correctly check if a contender is associated with a remote proof

Summary:
Contenders incorrectly checks if there is any remote proof status set for a proof but the intent was to check if the remote proof is present. This materializes into incorrect behavior when a node is restarted with persisted avapeers. The contender will improperly be promoted despite no remote proof being present.

Test coverage is not complete on the functional test side but that will be improved in a near future diff. For now we can be comfortable knowing the existing tests pass since they were written with the assumption that remote presence was being checked.

Depends on D18010

Test Plan:

ninja check
./test/functional/test_runner.py abc_p2p_avalanche_contender_voting

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D18011