Metal: Add labels and debug groups to help with GPU Debugging.

* Adds SK_ENABLE_MTL_DEBUG_INFO to enable labels and debug groups,
  dependent on skia_enable_gpu_debug_layers.

Bug: skia:12150
Change-Id: I5b4538c0f6df6ceed72d7e8e6f1952fd193b7b90
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/422756
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
14 files changed