Merge GrVkAttachment into GrVkImage. Bug: skia:12402 Change-Id: I743724f66db8d7666d4d627d6945ce6bc3dc6bc3 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/448261 Reviewed-by: Jim Van Verth <jvanverth@google.com> Commit-Queue: Greg Daniel <egdaniel@google.com>