Limit Premium Request Toggle

### Describe the feature or problem you'd like to solve

When using the auto-pilot feature, the amount of premium requests can go out of hand. Therefore a "max amount" of allowed premium requests would be nice.

### Proposed solution

Either as a cli toggle:
```bash
copilot --request-budget 2.5
```

Or as a slash command lile:
```bash
/budget 2.5
```

### Example prompts or workflows

_No response_

### Additional context

_No response_