[avalanche] Rename vote_records to blockVoteRecords in the processor

Summary:
Since we are going to vote on proofs, this makes the vote record content type more explicit.

Ref T1854.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Maniphest Tasks: T1854

Differential Revision: https://reviews.bitcoinabc.org/D10223