(D2D) clip<RoundedRect> is expensive

[smmalis37]

Admittedly my test case (https://github.com/smmalis37/sudoku_rust) with over 700 labels visible at once may be a bit extreme, but this shows up in profiling as one of the most expensive functions throughout the whole app. This is due to a combination of things:

• path_from_shape itself is expensive, spending lots of time in CreatePathGeometry, PathGeometry::Open and GeometrySink::close
• both CreateLayer and PushLayer take up a lot of time
• dropping the PathGeometry and the Layer at the end of the function are also surprisingly expensive

[smmalis37]

MSDN has this to say: "In general, you should create geometries once and retain them for the life of the application, or until they need to be modified."

https://docs.microsoft.com/en-us/windows/win32/api/d2d1/nn-d2d1-id2d1geometry