Revert "Reland "Revert "Omit dead SkSL functions"""

This reverts commit a15f2bfb6f6e15fbe08821895a070e23d234a3d0.

TBR=bsalomon@google.com, brianosman@google.com

Change-Id: I64cc7830281ee69bf3377c5b6daa3d96ccf4769e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293976
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
9 files changed