[clang] [clang][analyzer] Update CallDescription of 'tmpfile' & 'fopen' in StreamChecker (PR #70540)

[Balazs Benics via cfe-commits]

https://github.com/steakhal requested changes to this pull request.

Still looks good to me.
I recommended a couple comments here and there to clarify the intent of the test, and to raise awareness.

I'd suggest to reword the PR title (and the commit title ofc) to something like
`[analyzer] Restrict fopen and tmpfile modeling to POSIX versions in StreamChecker`


I'd also suggest renaming the `clang/test/Analysis/stream-wild-function.c` file to something more descriptive like `clang/test/Analysis/non-posix-stream-functions.c`

https://github.com/llvm/llvm-project/pull/70540