[clang] [CIR] Lower undef and poison initializers of any type in CXXABILowering (PR #230901)

[Arseniy Obolenskiy via cfe-commits]

aobolensk wrote:

> Looks reasonable to me, but I am not sure I fully comprehend the implications of moving the undef/posion initializer lowering to earlier.

The lowering of undef/poison is correct, but it was performed only in case of `if (auto recordTy = mlir::dyn_cast<cir::RecordType>(ty))`

So before my patch undef/poison were acceptable only as a part of the struct (field), but now they are lowered this way in any case

https://github.com/llvm/llvm-project/pull/230901