Use a separate row for store scaling in the monitor

## Feature Request

### Describe your feature request related problem

Sometimes we may encounter the problem that the store can not be offline for a long time, but we don't know the reason. It's usually caused by unhealthy regions that cannot be migrated.

### Describe the feature you'd like

We can provide a separate row for store scaling in the monitor to show the region's health for in the offline store and the estimated time for scaling.

- [ ] add region health status for offline
- [ ] provide the estimate time for offline
- [ ] change `pd.json` to add a row for scaling

Besides these, we can support more in the future.

### Describe alternatives you've considered

### Teachability, Documentation, Adoption, Migration Strategy