Move more utils into SkFontPriv, IWYU

Fissioned from https://skia-review.googlesource.com/c/skia/+/185460

Bug: skia:
Change-Id: Iaf980e931c17196f917602fc58fc39ab51e3d248
Reviewed-on: https://skia-review.googlesource.com/c/185840
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>
25 files changed