Move VkYcbcrSamplerHelper to its own files

The intent is to reuse this helper to create a YCbCr GM.

Change-Id: I4d6af42745dbf845e28753bec670ad4a75c393b2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/295443
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed