feat(linux): When kmp.json languages empty, fallback to .kmx languages

From review of #1585
> if languages wasn't set, to have the following fallbacks:
> * Fallback to .kmx language (`ethnologuelanguages`, `language`, and `windowslanguages` stores... Many older keyboards have good language data)
> * ~Then fallback to user's language~
> * ~Finally if that can't be found, fallback to `en`~

Currently, python doesn't have access to the internals of the kmx