Previously we deduced it was a block-relay-only based on presence of the
m_tx_relay structure. Now we have the ability to identify it directly via a
connection type accessor function.
This is a backport of core#19724 [6/9]
https://github.com/bitcoin/bitcoin/pull/19724/commits/1e563aed785565af6b7aed7f7399c52205d8f19c
Depends on D9774