Redis exporter enabled label

<!-- Please answer these questions before submitting your feature request. Thanks! -->

Is your feature request related to a problem? Please describe.

<!-- A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] -->

When enabling redis exporter no new label is set which could be used for scraping.

Describe the solution you'd like

<!-- A clear and concise description of what you want to happen. -->

A simple label, such as redis.opstreelabs.monitoring: "true" could be added when the exporter is added to the setup to make scraping easier

What version of redis-operator are you using?

redis-operator version: v0.18.0