Use SkGlyphRunListIterator in gpu

Instead of using the text blob through the stack start
using the glyph run list.

This CL is similar to a portion of https://skia-review.googlesource.com/c/skia/+/137224
which was reverted.

Change-Id: I1f0619bd2d13523f9af1a68ab27fb26abd086add
Reviewed-on: https://skia-review.googlesource.com/141543
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
9 files changed