Add an initContainer to the Synapse Deployment to copy the homeserver.yaml to /data

[mgoerens]

Currently, the homeserver.yaml lives in the ReadOnly ConfigMap mount point. Although ReadWrite access is not required by Synapse to run, it would be convenient to be able to edit the configuration manually for debugging purposes.

We should add an initContainer for copying the configuration file from the ReadOnly ConfigMap mount point (/data-homeserver) to the PV (mounted on /data).