Remove GrBackendSurfaceMutableState

Clients are now using skgpu::MutableTextureState directly

Bug: b/296240795
Change-Id: Ia310e876d49835ba8046f69372a8db0be30d14ff
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/744256
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
5 files changed