Reduce the memory usage in system_server

SystemFonts and related classes are now aggressively used in system
server. To reduce the memory impact, use ArrayMap/Set instead of
HashMap/Set.

Also, the language tags are duplicated in two places, one in Java and
one in Native object. Remove Java reference.

Bug: 178472803
Test: N/A
Change-Id: Id94b68bd34a1958fda67512dcdc683b20b12003f