remove SubRun from addGlyphToAtlas

This change is in preparation for moving addGlyphToAtlas
to GrAtlasManager.

Change-Id: Ic51ad565cc7ccd928a5f4304bf1801ec60f01fb0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293854
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed