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

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

I think the support for modules in clangd is pretty important. I posted https://discourse.llvm.org/t/rfc-directions-for-modules-support-in-clangd/78072 and let's see if we can make some progress.

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