[Graphite] Move create/deleteBackendTexture off Context/SharedContext.

This now moves the public API to Recorder and the actual creation
functionality to ResourceProvider.

Bug: b/239822490
Change-Id: Ie849624b7581863cb9aeaf967f7379db7069234c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/569636
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Nicolette Prevost <nicolettep@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
14 files changed