Revert "Revert "Remove GrBackendRenderTargetDesc in favor of GrBackendRenderTarget.""

This reverts commit 807371c15bd742efb98a9df6e1dee73e8bda8af5.

Docs-Preview: https://skia.org/?cl=40260
Change-Id: I28e0434c455155ff39a5aaa4141abdf442474e87
Reviewed-on: https://skia-review.googlesource.com/40260
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
12 files changed