Delete old alert rules when moving rules between folders

[chenlujjj]

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

I updated the alert rule groups folder, e.g. from folder A to folder B, but found that the old rules are still in folder A. And since they're provisioned, I had to delete them one by one via API call.

Describe the solution you'd like
When updating rule groups' folder, the controller should delete the old rules.

[theSuess]

Thanks for reporting this. We will get around to this eventually, but if you'd be up to implement this yourself, we'd appreciate a PR.
The only constraint is to avoid storing any state around the current folder in status as that usually increases complexity

[chenlujjj]

@theSuess Sure, I'd like to work on this.