[skottie] Parser cleanup

Consolidate parsing utils into their own CU.

TBR=

Change-Id: Idbf6db5220135ba91df6ebefce3a241c6ec4af15
Reviewed-on: https://skia-review.googlesource.com/99721
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
9 files changed