Add a matrix and "_log2" variants to SkSL wangs_fromula_*

Bug: skia:10419
Change-Id: I67f4379f449b9e59356ed83fc6f33f451d3e87c2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/416076
Reviewed-by: Tyler Denniston <tdenniston@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed