[clang] [llvm] Disentangle DISubprogram ODR type method uniquing from metadata uniquing (PR #217042)

[Kristina Bessonova via cfe-commits]

https://github.com/chbessonova commented:

> Without this patch DISubprogram ODR uniquing is "always on", but it now only occurs while isisODRUniquingDebugTypes returns true (after enableDebugTypeODRUniquing is called)
If I got this right, other frontends / MLIR would get this silently disabled, right? Just want to be sure this is the intended way to go.

https://github.com/llvm/llvm-project/pull/217042