[graphite] Add system to support client caching of images

Bug: b/238756324
Change-Id: Idea51ba727b5f30fa9073690d25a754b933b0688
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/564196
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
17 files changed