[skottie] Parented camera support

Parent camera layer transforms apply to the camera itself, thus

  T_camera' = T_camera x Inv(T_parent)

To support this composition:

  - introduce sksg::Transform::MakeInverse()

  - allow selectable pre/post parent composition in
    AnimationBuilder::attachMatrix3D()

Change-Id: Ie70b36e4e9bb1b32e60893df5695bdc6c0dc0d00
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210422
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
9 files changed