[clang] [clang][analyzer] Add test cases for CTU-import failures (PR #188524)

[Arseniy Zaostrovnykh via cfe-commits]

necto wrote:

> As this is a large set of closely related test files, I would prefer creating subdirectories for them. For example I think it would be nice to do
> 
> * `clang/test/Analysis/ctu-diag-foo-bar.cpp` → `clang/test/Analysis/ctu-diag/foo-bar.cpp`
>   `clang/test/Analysis/Inputs/ctu-foo-bar` → `clang/test/Analysis/Inputs/ctu-diag/foo-bar` (or perhaps `clang/test/Analysis/ctu-diag/Inputs/foo-bar`?)
> 
> Note that the test infrastructure can seamlessly discover and execute tests in subdirectories, and I already used this e.g. when I reorganized the [ArrayBound tests](https://github.com/llvm/llvm-project/tree/main/clang/test/Analysis/ArrayBound).


> I agree that dumping all the tests into a single directory was a poor choice in the past.
> I'd prefer more separation. Especially for CTU because I'm personally not especually in favor of that technology.


fd46cbbb8be2 Move ctu-related tests into a dedicated directory

https://github.com/llvm/llvm-project/pull/188524