As a telemetry source, I may prefer (or be required) to use an instance identifier label other than _id. I'd like subscription watch to allow the instance ID to be configurable, so that I can provide telemetry to subscription watch.

This impacts a couple of places, namely:

• The default promql query template is hardcoded to _id.
• PrometheusMeteringController expects the _id label to be present.

Implementation:

• A key should be added to the queryParams objects used in swatch-product-configuration/src/main/resources/subscription_configs files: `instance_key`, with existing configs set to "_id".
• The templates in application-openshift-metering-worker.yaml should be updated to consult use this variable instead of hardcoding to "_id".
• PrometheusMeteringController should be updated to consult the configuration for instance_key rather than looking for an "_id" label.

QE Note: Replace _id from https://gitlab.cee.redhat.com/smqe/smqe-tools/-/blob/master/smqe_tools/telemeter.py