[clang] [C++20] [Modules] [Itanium ABI] Generate the vtable in the module unit of dynamic classes (PR #75912)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

Given this patch has another unexpected behavior in windows (https://github.com/llvm/llvm-project/issues/97447), I'd like to revert this temporarily to wait for the response from Windows devs and your reproducer @mizvekov 

https://github.com/llvm/llvm-project/pull/75912