Replace GrColor4h with SkPMColor4f

- Mechanical replacement of GrColor4h (used throughout Ops) with
  SkPMColor4f.
- API adaptation (to/FromGrColor -> to/From_BytesRGBA).
- Complete removal of FromFloats (source was already SkPMColor4f),
  and toFloats (setting uniforms can directly access .vec()).

Bug: skia:
Change-Id: I37eece1fa7ed2545dc6843e840d4cc3c60f19747
Reviewed-on: https://skia-review.googlesource.com/c/166620
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
51 files changed