[clang] Reland [C++20] [Modules] [Itanium ABI] Generate the vtable in the mod… (PR #102287)

[Cameron Angus via cfe-commits]

kamrann wrote:

@ChuanqiXu9 I tested the small repro I had for this issue on latest from `main` and everything appears to be fine. 

https://github.com/llvm/llvm-project/pull/102287