Address deprication warning

[matthiasschaub]

Description

refactor: address deprecation warning

pkgutil.get_loader(module_or_name) is deprecated since version 3.12,
will be removed in version 3.14: Use importlib.util.find_spec() instead.

importlib.util.find_spec() has been added in Python version 3.4.

test: rewrite unittests to by pytests and remove unused function

Corresponding issue

Closes None

New or changed dependencies

• None

Checklist

• I have ensured my branch is mergeable with main (e.g. through git rebase main if necessary)
• My code follows the style guide and was checked with pre-commit before committing
• I have commented my code
• I have added sufficient unit and integration tests
• I have added new Hurl regression tests and checked all existing tests
• I have updated the CHANGELOG.md

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