The intention for this API is to be used when presenting language names
to the user, e.g., in expression evaluation diagnostics or LLDB errors.
Most uses of `GetNameForLanguageType` can be probably replaced with
`GetDisplayNameForLanguageType`, but that's out of scope of this PR.
This uses `llvm::dwarf::LanguageDescription` under the hood, so we would
lose the version numbers in the names. If we deem those to be important,
we could switch to an implementation that hardcodes a list of
user-friendly names with version numbers included.
The intention is to use it from
https://github.com/llvm/llvm-project/pull/161688
Depends on https://github.com/llvm/llvm-project/pull/161804
2c3724419c