fix: address warnings in test_checkers

[terriko]

Description

It looks like we're still using some deprecated stuff from pkg_resources, which is understandable because cve-bin-tool is older than the current preferred way for handling certain things. But it's time to refactor and bring ourselves into the future! Here's the warnings:

=============================== warnings summary ===============================
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[apache-httpd-expected_results0]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[vim-vim-enhanced-expected_results53]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[ffmpeg-libffmpeg.so-expected_results8]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[libexpat-libexpat.so-expected_results17]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[openssh_client-ssh-keyscan-expected_results35]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[python-python3.8-expected_results44]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[node-bin/node-expected_results26]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[bind-libisccc-9.16.37-Debian.so-expected_results62]
  /opt/hostedtoolcache/Python/3.10.16/x64/lib/python3.10/site-packages/pbr/git.py:28: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
    import pkg_resources

test/test_checkers.py::TestCheckerVersionParser::test_filename_is[apache-httpd-expected_results0]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[vim-vim-enhanced-expected_results53]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[ffmpeg-libffmpeg.so-expected_results8]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[libexpat-libexpat.so-expected_results17]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[openssh_client-ssh-keyscan-expected_results35]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[python-python3.8-expected_results44]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[node-bin/node-expected_results26]
test/test_checkers.py::TestCheckerVersionParser::test_filename_is[bind-libisccc-9.16.37-Debian.so-expected_results62]
  /opt/hostedtoolcache/Python/3.10.16/x64/lib/python3.10/site-packages/pkg_resources/__init__.py:3142: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('google')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
    declare_namespace(pkg)

I don't offhand know what we need to change to, but you should be able to figure it out by searching and reading the docs including the links they provided in the warning message above.

To reproduce

Steps to reproduce the behaviour:

1. run pytest with longtests enabled: LONG_TESTS=1 pytest test/test_checkers.py

Expected behaviour: no warnings
Actual behaviour: the warnings above apear

Anything else?

Feel free to add any other context here.

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