[clang] [clang] Lower _BitInt(129+) to a different type in LLVM IR (PR #91364)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

Maybe add a helper somewhere to check "is this type a bitint wider than 128 bits"?

https://github.com/llvm/llvm-project/pull/91364