[clang-tools-extra] [clangd] [C++20] [Modules] Introduce initial support for C++20 Modules (PR #66462)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

@kadircet  Comments addressed. Maybe due to some github's issue, my replies are separated and didn't form a standalone list. Hope this won't make it harder.

https://github.com/llvm/llvm-project/pull/66462