Adapt TextLayoutCache for new Harfbuzz scripts

The Harfbuzz script setting was wired to HB_Script_Common for left-
to-right text and HB_Script_Arabic for right-to-left. This change
selects from additional scripts using some utility APIs from
Harfbuzz.

Change-Id: I34a6f1e0407c8d122bc968443948e7863d1f91ed