stage naming change in colorfilter

1. want to standardize on naming convention (matching shaders asA...)
2. want to eliminate legacy asColorMatrix with its 255 bias

Bug: skia:
Change-Id: I43258aa3a406b92a3246e13e5dd996fcc207c784
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210621
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>
8 files changed