Use kubernetes Services FQDN rather than IPs

[mgoerens]

Kubernetes associates an internally resolvable FQDN to each Service. It should be possible to use those FQDN rather than IP Addresses to connect the bridges and the homeserver together (i.e. replacing ip addresses with FQDN in all config files).

This would have following advantages:

1. Simplify code: waiting for the Service to be up, and querying its IP Address. FQDN should be deterministic given a Service Name, Namespace and cluster Name AFAIK.
2. Remove unnecessary information from Status: we currently use the Status to store the IP Addresses of the Services for Synapse and for the Bridges (ClusterIP). The user shouldn't need this information.