[tests] Rename NodeConn and NodeConnCB
Summary:
NodeConn -> P2PConnection
NodeConnCB -> P2PInterface
Backport of core PR11791
Depends on D2361
Test Plan:
./test/functional/test_runner.py --extended
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Subscribers: teamcity, schancel
Differential Revision: https://reviews.bitcoinabc.org/D2362