Change to kAllFlags for RG8Unorm in Dawn/Mtl caps

This change updates graphite Dawn and Metal Caps to support kAllFlags
for RG8Unorm format. This follows from similar support for R8Unorm
and other formats which also support kAllFlags = Texturable,
Renderable, MSAA, Resolve and Storage flags from previously only
Texturable flag.

Bug: chromium:1430206
Change-Id: I71889b5f2b1bca3a45844be7539af49e62861177
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/704939
Commit-Queue: Saifuddin Hitawala <hitawala@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
2 files changed