[graphite] Add TextureProxy support.

With this change it should now be safe to start using Proxys and Textures
everywhere. There is no caching the Proxys/Textures will live as long as
someone holds a ref.

Bug: skia:12466
Change-Id: I3c657b65b44b9dca0a77a255d6a4fc89e3862124
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/456916
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
6 files changed