Remove hardcoded typeface pointers

There were a number of extraneous typeface pointers, one per
language, in TextLayoutCache.  Removing these makes adding additional
supported fonts easier.  This checkin now properly
unrefs typefaces returned by SkCreateTypefaceForScript.  Additionally,
all harfbuzz shaped fonts (with exceptions Greek, Cyrillic, Hangul)
should call SkCreateTypefaceForScript.

Change-Id: I7dcf603a89e5ff52c6dab8fb87ae1807a79c351c