Migrate GetLoopUnrollInfo out of SkSLAnalysis.

Change-Id: Ic0d1b04ee09a144dbb13cc98dff8e10409186a8e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/456648
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
3 files changed