Grafana Alerting: Inability to select a provisioned evaluation group when creating a new alert rule

### What happened? We've started using Grafana Alerting, and use provisioning to have all of our alerts in git. They're synced using GitOps and the Grafana sidecar nicely picks them up. As part of this workflow we generally create new alerts in the UI for testing, and export and check them into git afterwards. When configuring the evaluation behavior for a newly created alert through the UI, we're unable to select a provisioned evaluation group. It's simply greyed out: <img width="722" alt="Image" src="https://github.com/user-attachments/assets/cedde408-75b5-4a61-ac2e-7c6a68b418e9" /> ### What did you expect to happen? Is there any particular reason as to why we can't select provisioned evaluation groups for non-provisioned rules? If so, is there a workflow we're missing here that might work better? ### Did this work before? Not to my knowledge. ### How do we reproduce it? 1. Have some provisioned alerts. 2. Create a new rule in the same folder. 3. Attempt to select an existing evaluation group. ### Is the bug inside a dashboard panel? _No response_ ### Environment (with versions)? Grafana: v11.3.1 ### Grafana platform? Kubernetes ### Datasource(s)? _No response_