[avalanche] Split the abc_p2p_avalanche_proof_voting test into sub-cases

Summary:
There is no change in behavior. Next step is to merge the other voting test into a single test file.

Depends on D11043.

Test Plan:

./test/functional/test_runner.py abc_p2p_avalanche_proof_voting

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D11044