[Clang][CodeGen] `__dynamic_cast` should care about `type_info`'s address space

`__dynamic_cast` relies on `type_info`, which its signature assumed to be in the generic / default address space. This patch corrects the oversight (we know that `type_info` resides in the GlobalVar address space)  and adds an associated test.

Reviewed By: yaxunl

Differential Revision: https://reviews.llvm.org/D155870