[Enhancement] Progressbar handlers should use Paint

## Summary
We added #2250 but we used Color instead of Paint for now, we should implement the handler using the `Paint` type so we can do gradients etc

## API Changes

```
public interface IProgress : IView
{
Paint ProgressColor { get; }
}
```

## Intended Use Case

Allow to have a ProgressBar with gradient paint or future kinds of `Paint`

Review the progressbar handler work introduced by #2250 and the IProgress API shown in this issue. Trace the handlers that currently use Color and determine the relevant tests or samples for progress rendering. Done means the handlers use Paint through the exposed ProgressColor API and the intended gradient use case is covered.

Written by the indexing model from the issue text.