[llvm] [DebugInfo] Move `codeview::SourceLanguage` enumerators to CodeViewLanguages.def (NFC) (PR #141750)

[Reid Kleckner via llvm-commits]

rnk wrote:

I'm in favor. I think it's kind of inevitable that all large/important enums end up as x-macros, because at the end of the day, most enums need to be printed textually, and x-macros are the main way to do that without repeating the names.

https://github.com/llvm/llvm-project/pull/141750