TextLayoutCache - fix diacritics composition

- normalize (with ICU) each BiDi run before shaping them

We are normalizing by "chuncks" and starting from the end of the string. Each "chunck"
is composed of the main code point and its associated diacritics.

Fix bug #5738435 TextLayoutCache should be able to take care about diacritics during shaping

Change-Id: I7288027a7fa8eafb8b9f38d449625be60214548a