[avalanche] Unify finding a hash in poll into can_find_inv_in_poll via avatools

Summary:
This function has been copy-pasted around a few times without major modifications.
There are improvements we can make to it, so it is best to do it in one place.

Test Plan:

ninja && ./test/functional/test_runner.py abc_p2p_avalanche_* abc_rpc_isfinal

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13658