[skrive] Start parsing the node hierarchy

TBR=
Change-Id: I601ad831e69fd26ac8a0fe1f90ce2e9588a7f912
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/297056
Commit-Queue: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
11 files changed