[clang] [CIR] [Upstream local initialization for ArrayType (PR #132974)

[Amr Hesham via cfe-commits]

AmrDeveloper wrote:

> I'm not suggesting errorNYI. I'm suggesting op.emitError(). We can't do that here either, but maybe we could do it in the function from which this is called?

I think it's easier to keep it as assert, llvm_unreachable or a missing features as the error message mention, because otherwise we will modify the function to return nullptr to flag this case and also to modify the caller to catch it and report, also we don't have Operator to use it to emitError, what do you think? @andykaylor 

https://github.com/llvm/llvm-project/pull/132974