Avoid distutils imports in tests

[hroncok]

Description

When running pip's tests, it still imports from distutils directly. I'd like to work on a PR that will remove or conditionalize this dependency.

To check, I've used Python 3.11 with distutils removed.

First, I get:

$ nox -e test-3.11
ImportError while loading conftest '/home/churchyard/Dokumenty/pypa/pip/tests/conftest.py'.
tests/conftest.py:41: in <module>
    from tests.lib import DATA_DIR, SRC_DIR, PipTestEnvironment, TestData
tests/lib/__init__.py:42: in <module>
    from tests.lib.venv import VirtualEnvironment
tests/lib/venv.py:11: in <module>
    import virtualenv as _virtualenv
.nox/test-3-11/lib/python3.11/site-packages/virtualenv.py:24: in <module>
    import distutils.spawn
E   ModuleNotFoundError: No module named 'distutils'

Then I upgrade virtualenv, edit tests/requirements.txt, and skip some tests due to #8273

$ pytest_k='not test_from_link_vcs_with_source_dir_obtains_commit_id and not test_from_link_vcs_without_source_dir and not test_should_cache_git_sha'
$ nox -e test-3.11 -- -k "$pytest_k" --deselect tests/functional --deselect tests/lib/test_lib.py --deselect tests/unit/test_build_env.py
...
==================================== ERRORS ====================================
______________ ERROR collecting tests/functional/test_install.py _______________
ImportError while importing test module '.../pypa/pip/tests/functional/test_install.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/lib64/python3.11/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/functional/test_install.py:1: in <module>
    import distutils
E   ModuleNotFoundError: No module named 'distutils'
___________ ERROR collecting tests/functional/test_install_wheel.py ____________
ImportError while importing test module '.../pypa/pip/tests/functional/test_install_wheel.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/lib64/python3.11/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/functional/test_install_wheel.py:3: in <module>
    import distutils
E   ModuleNotFoundError: No module named 'distutils'

I'd like to avoid the imports entirely, even though the 2 test files probably cannot run with the new virtualenv anyway (yet).

Expected behavior

Tests still run on Python without distutils.

pip version

main

Python version

3.11.0rc2 sans distuils

OS

Fedora Linux

How to Reproduce

See the description.

Output

No response

Code of Conduct

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