onProgram for overdraw-colorfilter

+ add Builder: min(I32), max(I32), gatherF()

Incidental bench timings (iMac Pro):
- RP:          350
- gatherF:     210
- unpack_8888: 187

Change-Id: I1d09f76206e89cd595a9e42c4b96bbf2f53ab86c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/279736
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
5 files changed