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

[Jeremy Morse via cfe-commits]

https://github.com/jmorse commented:

Sounds good for the bits I commented on; I'd wait for @dzhidzhoev 's feedback though.

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