[clang] [C++20] [Modules] Embed all source files for C++20 Modules (PR #102444)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> Was this discussed/reviewed/motivated? There are drawbacks to this approach outlined in #72383
> 
> @iains @jyknight @AaronBallman @Bigcheese

The motivation is in https://github.com/llvm/llvm-project/issues/72383 and I comment in https://github.com/llvm/llvm-project/issues/72383#issuecomment-2275135890

This is not reviewed. I wait for several weeks but got no response. And I think it is good. So I choose to land it.

https://github.com/llvm/llvm-project/pull/102444