Use clipping when layer bounds are too small to mirror the crop's corner

If the corners of the bounds only partially align with the crop we need
to ensure that the resulting shape can still be represented as a round rect.
This CL accounts for the fact that the round rect implementation will recompute
the value of the corner radius if the radius is greater than the width or
height to which it is applied.

See https://www.w3.org/TR/css-backgrounds-3/#corner-overlap

Test: atest librenderengine_test
Bug: 145094543
Change-Id: I48d04ea726e8765de0e300c2608ed5c4e6fe6bbc