This was flagged years ago as a potential performance hotspot: each
locale is loaded at process start for any kmcomapi-involved process,
which takes quite a long time. This refactor moves the locale
enumeration out of kmcomapi and into the build process, so we have a
static list of locales put into locale/index.xml.
This includes a minor breaking change to Keyman Engine API on Windows:
`MessageFromID(id, locale)` now only allows the three ids
SKUILanguageName, SKUILanguageNameWithEnglish, and SKLanguageCode, for
performance reasons. At this point, only SKUILanguageNameWithEnglish is
actually used anywhere in Keyman, and it is unlikely that any other
consumers are requesting alternate IDs.
Fixes: #14787
Build-bot: skip release:windows
