[clang] [CIR] Fix reference alignment to use pointee type (PR #186667)

[Henrich Lauko via cfe-commits]

xlauko wrote:

> Can you convince me this is the right change? We're agreeing with classic-codegen on all the examples, and this patch makes that no longer true. We should be agreeing with classic-codegen.

@erichkeane no we were not agreeing on the alignment before, this change aligned us with classic codegen (at least I tried). The differences that you see are caused by `byval` parameters that CIR does not support yet.

https://github.com/llvm/llvm-project/pull/186667