[skottie] Initial support for per-character 3D

When per-character 3D is enabled, text properties can be animated in
3 dimensions.

 - position and scale become 3-value vectors
 - in addition to existing "r" (really rz), rotation gains "rx" and "ry"
 - instead of specializing for 3D, expand the existing structures to
   handle both 3D and 2D modes
 - also ensure that sksg::Transform does not flatten to SkMatrix

Change-Id: I426a7ee1ff38c1702deb85e9f1db80f6069f36d6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/272648
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
8 files changed