Consider priority to schedule hot regions of smaller size with others same

## Feature Request

### Describe your feature request related problem

The smaller region generates snapshots faster, avoiding snapshots getting stuck and taking up the hot-region-schedule-limit, which would prevent other hot regions from being scheduled.

This will also have less impact on store size.

### Describe the feature you'd like

consider priority to schedule hot regions of smaller size with others same

### Teachability, Documentation, Adoption, Migration Strategy

Go, hot-region-scheduler