[tempo-distributed] Add granular control for metaMonitoring.serviceMonitor

[HummingMind]

Hello,
It looks like at the moment the only way to enable ServiceMonitors would be to set metaMonitoring.serviceMonitor.enabled=true.

This seems to create the following Prometheus Operator Service Monitors:

Can you please allow individual control over creation of these? Just a true or false for each one?

For example, I don't use the metrics-generator and the tempo-query in my cluster/setup.
So, I would not want to create the ServiceMonitors for these two so they don't show up in Prometheus Service Discovery / Targets.

Thank you!