(created using eb --new-pr)

There are rare cases where a Python package provides path configuration files to set-up some state for the package to work correctly. One such example was recently encountered in easybuilders/easybuild-easyconfigs#24081: numba-cuda.

Numba has deprecated their CUDA bindings. Instead, NVIDIA provides bindings which hook into numba. The installation is entirely separate. However, they provide a path configuration file (.pth) which basically overwrites the include for numba.cuda.
Typically, these files only work when they are in a system directory checked by Python. This is the case in a venv or in a user/system wide installation. In EasyBuild however, this fails. Writing our own sitecustomize.py for numba-cuda would shadow the one provided in EasyBuild. For this to work, we require EBPYTHONPREFIXES, as our sitecustomize.py adds the directories to the site dir, therefore being considered by Python

This PR implements these changes:

1. Refactor the logic to determine if we need EBPYTHONPREFIXES into its own function using_ebpythonprefixes
2. Add a check if this is required, by checking the install directory and, if needed, the test install directory.
3. Use this refactored method in make_module_extra and test_step to check if we need EBPYTHONPREFIXES.

Marked as draft until I was able to verify that these changes work. Unfortunately, none of my systems are using EBPYTHONPREFIXES, making test reports like easybuilders/easybuild-easyconfigs#24081 (comment) harder to reproduce.