LibUnicode: Generate the entire locale likely-subtags dataset

The amount of aliases in the likely-subtags dataset is quite large, so
this also needed to change the way the data is generated. Otherwise, the
compiler would complain about the size of the generated code.

Previously, a static method was generated that would effectively parse
the dataset into a HashMap of Unicode::LanguageID at runtime. We now
perform that parsing at generation-time, and instead generate an Array
of a structure similar to Unicode::LanguageID (we cannot use the same
structure because it contains String and Optional, which cannot be used
at compile-time).

Author: trflynn89