That's what this class really is; in fact that's what the first line of
the comment says it is.
This commit does not rename the main files, since those will contain
other time-related classes in a little bit.
In CLDR 42 and earlier, we were able to assume all cldr-localename files
existed for every locale. They now do not exist for locales that don't
provide any localized data. Namely, this is the "und" locale (which is
an alias for the root locale, i.e. the locale we fall back to when a
user provides an unknown locale).
Further, we were previously able to assume that each currencies.json in
cldr-numbers contained all currencies. This file now excludes currencies
whose localized names are the same as the currency key. Therefore, we
now preprocess currencies.json to discover all currencies ahead of time,
much like we already do for languages.json.
In order to prevent this commit from having to refactor almost all of
Intl, the goal here is to update the internal parsing/canonicalization
of locales within LibLocale only. Call sites which are already equiped
to handle String and OOM errors do so, however.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
