Allow using $__rate_interval in Panel Title

### # What went wrong? Would it be possible to enable using the $__rate_interval built-in variable in Panel Title? For the same reason $__interval and $__interval_ms were enabled in https://github.com/grafana/grafana/discussions/36990 We expect to also use the rate interval inside the panel title. This variable is currently the used one in most of our Prometheus queries ### # How do we reproduce it? add this variable inside panel title ### # What Grafana version are you using? Grafana v9.5.1 (bc353e4b2d) ### ## Optional Questions: ### Is the bug inside a Dashboard Panel? Copy the panel's ["get-help" data](https://grafana.com/docs/grafana/latest/troubleshooting/send-panel-to-grafana-support/) here ### Grafana Platform? None ### User's OS? _No response_ ### User's Browser? _No response_ ### Is this a Regression? None ### Are Datasources involved? _No response_ ### Anything else to add? _No response_