Use an external Loki with the UIPlugin

[sylapr]

Currently the UIPlugin only works with a LokiStack installed on OpenShift.

We are currently using the ClusterForwarder and are forwarding to an external Loki stack outside the cluster to consolidate multiple clusters. It would be easier if we could connect this plugin to this external stack and have the same features as a local stack.

It's still the same data as we don't transform data. The mechanism would be the same but with a custom URL and authentication.