[clang] [clang][modules] Headers meant to be included multiple times can be completely invisible in clang module builds (PR #83660)

[Ilya Biryukov via cfe-commits]

ilya-biryukov wrote:

@ian-twilightcoder this change seemed to cause our internal builds to run out of source location space.
```
remark: source manager location address space usage: [-Rsloc-usage]
note: 408559B in local locations, 2146921126B in locations loaded from AST files, for a total of 2147329685B (99% of available space)
```

The main offenders from the 

https://github.com/llvm/llvm-project/pull/83660