Use cached [compact] blocks to respond to getdata messages

Summary: Backport of core PR9665

Test Plan:

make check
./test/functional/test_runner.py p2p_compactblocks

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2620