Plumb GrColorType through all ops/processors that sample textures.

This change also allows for the remove of GrPixelConfigIsOpaque function.

Bug: skia:6718
Change-Id: I7e7b70f02d911eda67640d648fb6348091e0f55d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/248698
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
65 files changed