Move SkTTopoSort to src/gpu and rename it to GrTTopoSort

Change-Id: I76deff6bbb2d796cead0e9415c19daf5edceaa73
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/335296
Reviewed-by: Adlai Holler <adlai@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
6 files changed