Add support for InputRRect as Group's clip

[terrysahaidak]

Description

Thanks for adding support for nonuniform rounded rects. In my use case, we have to reuse the same rect for both rect and clip. Currently, i have to maintain both path and rect to pass the same thing to either rect or clip (which accepts rect).
Would be amazing if clip would also accept InputRRect so we don't need to create a path for it.

I didn't dive deep in the code base so the question: can InputRRect be used as clip for groups at all?

[wcandillon]

clip does accept a rect, rounded rect, or path.
If this is not working on your side, let me know and we will reopen this.