Loki Operator does not properly update LokiStack metrics

Description of problem:

The current implementation of the LokiStack metrics emitted by Loki Operator sometimes keeps old versions of the metrics. This leads to the metrics not properly reflecting the current state of the deployed LokiStack resources.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:

1. Install Loki Operator and deploy one or more LokiStack resources
2. Remove LokiStack resources or change configuration (for example: size)

Actual results:

"lokistack_" metrics exposed by Loki Operator contain outdated information about deployed LokiStack instances.

Expected results:

"lokistack_" metrics should only contain information that reflects the current state of the cluster.

Additional info:

As we're currently not using any of the metrics, except for one of our own alerts, it might make sense to completely replace the current set of metrics with new ones.