This CL also adds tests for vector*scalar and scalar*vector folding.
We currently do not constant-fold these, but support will be added in a
followup CL.
Change-Id: I68d7374ae15ab2f4d805a095803b645c92fb03d9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/352237
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
