split abc-p2p-fullblocktest into sigops and non-sigops parts

Summary:
Like with D5060, it makes sense to split out the sigops part of
this test since we're planning to deactivate sigops, and this lets
us independently deal with sigops.

Test Plan: ninja check-extended

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5062