Rounded Corners

### Description

As on now, most of the controls where CornerRadius is needed, we have set the default value that's defined in Fluent theme styles by using `Border.CornerRadius` property in style, however this is not customizable and developers cannot set is as follows :
```

...
```

The only way that can be used right now is as follows :
```

<Setter Property="Border.CornerRadius" Value="8" />

```
This will make it tougher for developers to customize corner radius. Here are the next steps / work items that need to be done regarding this task.

**Primary Tasks**
- [x] Prioritize controls where rounded corners add more visual value
- [ ] Finalize a way to allow customizing CornerRadius for controls other than Border

**Secondary Tasks**
- [ ] Write performance measurement benchmark for rounded corners.
- [ ] For container controls - Check performance impact.

### Notes:

- CornerRadius Property and Converter already existing for wpf.
- For button and some other controls this property is not Present in the backing cs file. We might need to add this property to those controls. [API Change]
- We might not want to have CornerRadius property in all the xaml file with the same values to avoid duplication.
- We can have a list of variables, which contains the cornerradius values, and we can set CornerRadius property with this value as a DynamicResource.
- Performance needs to be assessed per control and multiple controls on the same window and for different categories of controls like container controls, nested controls.

### Open Questions:
- Clarify what happens when the Dev overrides the cornerRadius attribute in the app?