pytest-virtualenv fails tests on Python 3.12

[mgorny]

(after fixing pytest-shutil via #219)

============================================================== FAILURES ===============================================================
_______________________________________________________ test_installed_packages _______________________________________________________

    def test_installed_packages():
        with venv.VirtualEnv() as v:
>           ips = v.installed_packages()

v          = <pytest_virtualenv.VirtualEnv object at 0x7f1db7343c80>

tests/integration/test_tmpvirtualenv.py:15: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
pytest_virtualenv.py:227: in installed_packages
    lines = self.run([self.python, "-c", code], capture=True).split('\n')
        code       = ('from pkg_resources import working_set\n'
 "for i in working_set: print(i.project_name + ' ' + i.version + ' ' + "
 'i.location)')
        package_type = 'ANY'
        res        = {}
        self       = <pytest_virtualenv.VirtualEnv object at 0x7f1db7343c80>
pytest_virtualenv.py:151: in run
    return super(VirtualEnv, self).run(args, **kwargs)
        __class__  = <class 'pytest_virtualenv.VirtualEnv'>
        args       = [Path('/tmp/portage/dev-python/pytest-virtualenv-1.7.0-r2/temp/tmpcd8n598l/.env/bin/python'),
 '-c',
 'from pkg_resources import working_set\n'
 "for i in working_set: print(i.project_name + ' ' + i.version + ' ' + "
 'i.location)']
        kwargs     = {'capture': True,
 'env': {[...]}}
out        = ('Traceback (most recent call last):\n'
 '  File "<string>", line 1, in <module>\n'
 "ModuleNotFoundError: No module named 'pkg_resources'\n")
p          = <Popen: returncode: 1 args: ['/tmp/portage/dev-python/pytest-virtualenv-1.7....>
self       = <pytest_virtualenv.VirtualEnv object at 0x7f1db7343c80>
shell      = False

/usr/lib/python3.12/site-packages/pytest_shutil/workspace.py:132: CalledProcessError
-------------------------------------------------------- Captured stdout call ---------------------------------------------------------
created virtual environment CPython3.12.0.beta.1-64 in 445ms
  creator CPython3Posix(dest=/tmp/portage/dev-python/pytest-virtualenv-1.7.0-r2/temp/tmpcd8n598l/.env, clear=False, no_vcs_ignore=False, global=False)
  seeder FromAppData(download=False, pip=bundle, via=copy, app_data_dir=/tmp/portage/dev-python/pytest-virtualenv-1.7.0-r2/homedir/.local/share/virtualenv)
    added seed packages: pip==23.1.2
  activators BashActivator,CShellActivator,FishActivator,NushellActivator,PowerShellActivator,PythonActivator
---------------------------------------------------------- Captured log call ----------------------------------------------------------
ERROR    pytest_shutil.workspace:workspace.py:130 Stdout/stderr:
ERROR    pytest_shutil.workspace:workspace.py:131 Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'pkg_resources'

Apparently it assumes that pkg_resources package will be available in the freshly created virtualenv which is no longer the case with Python 3.12 (setuptools is no longer included in new virtualenv, just pip).