Replace pkg resources use

[loqs]

• setup.py: except ImportError for missing pkg_resources
  • Missing pkg_resources indicates setuptools 82 or newer which is more recent that than 18.5 so the version check using pkg_resources can safely be skipped.
  • This is an alternative to setup.py: handle missing pkg_resources import #592 that avoids using setuptools internal namespace setuptools._vendor.packaging.version.
  • Fixes setuptools > 81 doesn't include pkg_resources #593.
• conftest.py: Replace pkg_resources use with packaging
  • This is python 3+ only and intended to be merged after Only support python versions that receive security updates #580
  • I can refactor it so it supports 2.7+ if desired.

[hroncok]

Thank you.

[loqs]

@hroncok appveyor appears to be failing for two reasons:

• py27-optional fails because "Microsoft Visual C++ 9.0" was removed from the "Visual Studio 2022" image which is needed to compile lxml-5.0.2.
• py37-base and py37-optional fail because the Python 3.7 support was removed from the "Visual Studio 2022" image so tox can not run on it.

The py27-optional may be fixable by switching to the "Visual Studio 2015" image. Python 3.7 might require using a source build.