Changing the way we select a grapheme

Selecting only graphemes that are fully inside the
[start:end) range. Hopefully, it's a temporary
solution to simplify SkParagraph vs TxtLib comparison.

Change-Id: Iebc74fb4ae20c232bfae762a04e45f0979cf6236
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/322438
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Julia Lavrova <jlavrova@google.com>
5 files changed