Refactor LearningRateMonitor

Outline & Motivation

• self.last_momentum_values does not seem needed, but I may be overlooking something.
• Instead of returning the name with -momentum suffix when logging betas, just log it with -beta suffix.
• If logging betas, log all of them. The name could therefore be -beta0, -beta1 in the case of Adam.
• Change the current logging names, e.g., lr-Adam to optimizer-Adam-lr and lr-Adam-momentum to optimizer-Adam-momentum (it doesn't have momentum this is just for demonstration, it would actually be optimizer-Adam-beta0, optimizer-Adam-beta1).
• remove the log_momentum argument as it can be inferred automatically.

Pitch

Happy to open a PR with these changes.

Additional context

No response

cc @borda @justusschock @awaelchli