converted GrConfigConversionEffect to SkSL

Bug: skia:
Change-Id: If17cf0fc8b857d22f33a462a39a02bcddd15deda
Reviewed-on: https://skia-review.googlesource.com/55741
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
4 files changed