Adds more tests for the new "proxy" remote cluster connection mode, using a Docker-based
setup, as well as testing SNI-based routing using HAProxy.
- Checks that the new proxy mode can work in situations where the publish host of the nodes in
the remote cluster are not routable.
- Checks that the new proxy mode can work with clusters where nodes are hidden behind
HAProxy.
- Checks that the new proxy mode can work with clusters where nodes are hidden behind
HAProxy, using SNI to identify the nodes/cluster behind HAProxy.
Relates #49067
Yannick Welsch