add vec2 slot support to CanvasKit

vec2 is used for properties like scale, anchor, skew, and other positional data

Change-Id: I1b9178e4ff28f8a01b090b0a0f0b544bb5226786
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/740057
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Jorge Betancourt <jmbetancourt@google.com>
7 files changed