build: simplify generation of closure locale file (#42230)

In the past, the closure file has been generated so that all individual
locale files were imported individually. This resulted in a huge
slow-down in g3 due to the large amount of imports.

With 90bd984 this changed so that we
inline the locale data for the g3 closure locale file. Also the file
only contained data for locales being supported by Closure. For this a
list of locales has been extracted from Closure Compiler, as well as a
list of locale aliases.

This logic is prone to CLDR version updates, and also broke as part of
the Gulp -> Bazel migration where this logic has been slightly modified
but caused issues in G3. e.g. a locale `zh-Hant` was requested in g3,
but the locale data had the name of the alias locale that provided the
data at index zero (which represents the locale name). Note that the
locale names at index zero always could differentiate from the requested
`goog.LOCALE` due to the aliasing logic. This just didn't come up before.

We simplify this logic by generating a `goog.LOCALE` case for all
locales CLDR provides data for. We don't need to bother about aliasing
because with the refactorings to the CLDR generation tool, all locales
are built (which also captures the aliases), and we can generate the locale
file on the fly (which has not been done before).

PR Close #42230