net: Add CNode::ConnectedThroughNetwork member function

Summary:
This is a backport of core#19998 [2/3]
https://github.com/bitcoin/bitcoin/pull/19998/commits/49fba9c1aa699d3aa47ea4dafe07b47c8d0aac6e

Depends on D10456

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D10457