Stop flattening GrCoordTransforms in parent GrFragmentProcessors.

This changes moves to a model that iterates over GrCTs in a GrFP hierarchy when inserting transformations by GrGLSLPrimitiveProcessors.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2339203002

Committed: https://skia.googlesource.com/skia/+/d91237ee051523f439238042674ade99207fe4a6
Review-Url: https://codereview.chromium.org/2339203002
27 files changed