Consolidate Proxy caching code in GrResourceProvider

This doesn't implement the GrSurfaceProxy-based caching but just carves out a space for it.

Split out of: https://skia-review.googlesource.com/c/8823/ (Remove GrFragmentProcessor-derived class' GrTexture-based ctors)

Change-Id: Iec87b45e3264b349d7804f63e361e970b925e335
Reviewed-on: https://skia-review.googlesource.com/9626
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
19 files changed