Proposal

Currently, Prometheus Scaler requires a metricName which is used only for KEDA internal things (it's not sent to the prom server).
This requirement isn't necessary since we introduced mechanisms to ensure the unique metrics names inside the ScaledObject and we should make it optional and also deprecate it in favor of self-generated internal name

https://github.com/kedacore/keda/blob/main/pkg/scalers/prometheus_scaler.go#L128-L132