Migrate GrSurfaceContext readPixels to take direct context

After this lands we'll proceed up the stack and add the direct
context requirement to the public API and SkImage.

Bug: skia:104662
Change-Id: I4b2d779a7fcd65eec68e631757821ac8e136ddba
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/309044
Commit-Queue: Adlai Holler <adlai@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
30 files changed