[net processing] Do not request transaction relay from feeler connections

Summary:

[test] Add testing for outbound feeler connections

Extend the addconnection RPC method to allow creating outbound
feeler connections. Extend the test framework to accept those
feeler connections.

[net processing] Do not request transaction relay from feeler connections

Add a test to verify that feeler connections do not request transaction relay.

This is a backport of core#22777
Depends on D10944

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10945