Revert "Rename gl_SampleMask to sk_SampleMask"

This reverts commit 23716d42f730c62b3e198310a5cc1b324f6de4e1.

Reason for revert: red bots and GMs

Original change's description:
> Rename gl_SampleMask to sk_SampleMask
> 
> Change-Id: I3924c6f76edf310a984e4fd89478b00eeec69722
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/249931
> Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
> Commit-Queue: Chris Dalton <csmartdalton@google.com>

TBR=egdaniel@google.com,csmartdalton@google.com,ethannicholas@google.com

Change-Id: I74848e95972cf2c41cc28887e26214136ce79e08
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/250180
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
7 files changed