feat(developer): canonicalize language tags at compile time

Given the use of langtags.json, any bcp 47 tag in the .kmp and in .keyboard_info found in alternate tags should always be canonicalized at compile time to the primary tag. A hint may be provided also (so long as the hint can be disabled).

When this is implemented, provide a report to the keyboards repository for a one-time cleanup of language tags for existing keyboards.