Improve exposure of cluster location in admin console

When running in a cluster, it is convenient to know where on the cluster specific sessions live (either remotely, or on the local cluster node). Sessions include:

• Client sessions, both on the overview and in the detailed view (here, clustering information is already provided)

• S2S sessions, both on the overview and in the detailed view

• External component sessions, both on the overview and in the detailed view

• Chat room occupants

This information should only be displayed when clustering is available, to reduce the noise on systems where the feature is not used.