[skottie] Clean up SkottieProperties

Split into Adapter and Value CUs.

No real changes, just shuffling things around.

TBR=
Change-Id: I50eaeb3950f4c59e7d7027955b3f49ca2a346e59
Reviewed-on: https://skia-review.googlesource.com/116186
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
9 files changed