Extract a GrAATriangulator class

Bug: skia:10419
Change-Id: I0394697fdc292cabeb81da508e1acdc74e2127ff
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/350257
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
3 files changed