[graphite] Add CopyAsDraw helper to Image_Base

CopyAsDraw will be used explicitly in the single-texture Image as
a fallback when it can't blit, and will be the default copy
operation for Image_Base (to handle the YUVA code automatically).

Bug: b/333909822
Change-Id: If856cfaf39136e11c7292f9d389bfcd81d61acba
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/838098
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
3 files changed