[clang] [Clang] Implement P3034R1 Module Declarations Shouldn’t be Macros (PR #90574)

[via cfe-commits]

yronglin wrote:

> module foo(); should be Ill-formed.

Ahh, so case like the following also should be ill-formed:
```
#define FUNC_LIKE(X) function_like_##X
export module FUNC_LIKE(bar);
```
> we can get the module name of a TU by cat and grep

This means that no macros of any kind can appear in the module name.

Thank you all. Things much clearer now.

https://github.com/llvm/llvm-project/pull/90574