[graphite] Add SkImage::MakeGraphiteFromBackendTexture

This also updates SkSurface::MakeGraphiteFromBackendTexture to better parallel the new code.

Bug: b/249788181
Change-Id: I5c2bcabcba238813cb3da9e44cebf68e8b8a3ea0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/585969
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed