Move Language normalization code from Paint.cpp to Minikin.

The language code to BCP47 conversion is done by Minikin.

Also this CL addresses the signature changes by
I8df992a6851021903478972601a9a5c9424b100c

Bug: 26168983
Change-Id: I277a08b5a17d45c3edb8fb597fdf6786bbe9f83b