Clean up GrQuad ctors

Refactor Sk4f transformations into reusable internal function.
Switches the SkRect+SkMatrix ctor to a factory method.
Adds simple constructors for Sk4fs and SkRects w/o transforms.

Bug: skia:
Change-Id: I88a4a5f7304b1cf00d68c7772bb0fc19c97abee3
Reviewed-on: https://skia-review.googlesource.com/c/191569
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
8 files changed