Connect to peers with NODE_NETWORK_LIMITED flag

Summary:
This allow connecting to peers that have the flag set.
Complete p2p_node_network_limited.py test for the new
behavior.

Partial backport of core PR10387
commits 31c45a9, 6fe57bd, 3f56df5 and eb91835

Test Plan:

./test/functional/test_runner.py p2p_node_network_limited.py

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2390