Separate locales into more usable groups in the translation menu

Summary:
Ref T5267. Ref T4103. Currently, adding new locale support to the upstream fills this menu with confusing options which don't do anything. Separate it into four groups:

• Translations: these have a "reasonable number" of strings and you'll probably see some obvious effect if you switch to the translation.
• Limited Translations: these have very few or no strings, and include locales which we've added but don't ship translations for.
• Silly Translations: Pirate english, etc.
• Test Translations: ALLCAPS, raw strings, etc.

Czech is currently in "test" instead of "limited" for historical reasons; I'll remedy this in the next change.

Test Plan: {F1661523}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4103, T5267

Differential Revision: https://secure.phabricator.com/D15978