This repurposes much of our embedded SkFontMgr code
to take in data directly instead of from compiled-in
variables.
Also makes no_font and no_embedded_font work better.
Bug: skia:9469
Change-Id: Ibde49c9a448cfca79c5712aa9abbe15997a163d0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/244510
Reviewed-by: Ben Wagner <bungeman@google.com>