[androidkit] Add Skottie sample

Convert existing SkottieActivity to use a Skottie Sample, and also add
one to the cube demo.

Change-Id: I86193889d293ddd653b0cac7200e830fa873ea69
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/413736
Reviewed-by: Jorge Betancourt <jmbetancourt@google.com>
3 files changed