[analyzer] Accept C library functions from the `std` namespace (#84469)

Previously, the function `isCLibraryFunction()` and logic relying on it
only accepted functions that are declared directly within a TU (i.e. not
in a namespace or a class). However C++ headers like <cstdlib> declare
many C standard library functions within the namespace `std`, so this
commit ensures that functions within the namespace `std` are also
accepted.

After this commit it will be possible to match functions like `malloc`
or `free` with `CallDescription::Mode::CLibrary`.

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Co-authored-by: Balazs Benics <benicsbalazs@gmail.com>