Reland "change matrix_2x3 to row-major"

This is a reland of e023608611b69a7c20682846d4701d3133168cf0

I have expanded the scope of this CL because having multiple
versions of the same code was confusing me.

All updatable functionality has been moved to SkTransformShader.
I made SkUpdatableShader implement the SkStageUpdater allowing
SkTransformer to act as both types of updater.

Original change's description:
> change matrix_2x3 to row-major
>
> Change-Id: Id25b3875f54f359bac90b6d3a7695287fc108b64
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/456467
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Herb Derby <herb@google.com>

Change-Id: I3326d8ea2c6fa9dabca8021a746600b4649933e7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/456638
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
7 files changed