Simplify SkTypeface::charsToGlyphs API to require UTF32 input

Change-Id: I486713c496c40103eef13fa6068ac4d69e32f606
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207865
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
27 files changed