Expose intercepts on SkFont

Already exposed (on TextBlob), so this makes it available for clients
that may use drawGlyphs directly. (including canvaskit/flutter)

Change-Id: I8b4bd51e13827dc3970d5a6d06f0e0d3031af13c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/408638
Reviewed-by: Julia Lavrova <jlavrova@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed