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>
24 files changed