Implement D3D copySurface.

Also fixes a minor assert in GrD3DBuffer, and removes an unused dxgi format

Change-Id: I4aa533b5c514d573fc606622c28ea7e2181bd7cb
Bug: skia:9935
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/285499
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
6 files changed