[clang] [clang] Add `intrin0.h` header to mimic `intrin0.h` used by MSVC STL for clang-cl (PR #75711)

[Max Winkler via cfe-commits]

MaxEW707 wrote:

I will need someone to commit on my behalf since I do not have write access.

> lgtm, and good to land provided you do a quick re-check to confirm that this doesn't tank compile times now with that part included. Thanks!

The include times below are done with the following source file using a locally release build of clang, `-ftime-trace`, and msvc stl shipped with MSVC 1939.
```
#include <map>
#include <vector>
#include <memory>
```

clang-cl.exe without `yvals_core.h` shadowing takes ~1,344 ms in the frontend. `intrin.h` took ~955 ms to parse.

clang-cl.exe with `yvals_core.h` shadowing takes ~395 ms in the frontend. `intrin0.h` took ~1.4 ms to parse.

https://github.com/llvm/llvm-project/pull/75711