Reland "Make RGB_888x pixel operations work."

This is a reland of 8ce24b1d11f25a871fa23285cfd29373aa5d1d6a

Original change's description:
> Make RGB_888x pixel operations work.
>
> Also remove vulkan-specific conversions in GrVkGpu and rely
> on higher level SurfaceContext to convert correctly.
>
> Bug: skia:8862
> Change-Id: Ib8b0541c8c5831148b7129c4bbed3f925660116e
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/392378
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

Bug: skia:8862
Change-Id: I5d085e47398a4a2947228ee67f867552fa93123a
Cq-Include-Trybots: luci.skia.skia.primary:Test-Debian10-Clang-NUC5PPYH-GPU-IntelHD405-x86_64-Debug-All-Vulkan
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/392842
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
8 files changed