Replace setup.py versioning scheme with standard convention

[tomvothecoder]

• Closes installation in development conda env fails #893
• A workaround to the issue with setuptools>=6.6.0 enforcing PEP440 which was breaking the local package build process for pcmdi_metrics.
• Bumps isort pre-commit hook to fix a bug that breaks the GH Actions build.

Notes

When bumping pcmdi_metrics for a new release, make sure to update release_version in setup.py.

Also, local builds should be installed using python -m pip install . rather than python setup.py install.

Output

(pmp_dev) vo13@ml-9704174 pcmdi_metrics % python -m pip install .
Processing /Users/vo13/Documents/Repositories/PCMDI/pcmdi_metrics
  DEPRECATION: A future pip version will change local packages to be built in-place without first copying to a temporary directory. We recommend you use --use-feature=in-tree-build to test your packages with this new behavior before it becomes the default.
   pip 21.3 will remove support for this functionality. You can find discussion regarding this at https://github.com/pypa/pip/issues/7555.
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... done
Building wheels for collected packages: pcmdi-metrics
  Building wheel for pcmdi-metrics (PEP 517) ... done
  Created wheel for pcmdi-metrics: filename=pcmdi_metrics-2.5.1-py3-none-any.whl size=1697808 sha256=8eb25d25440ffa247bd2f35c26c212c68bf0cb25d82f6870d2a4e6f4bac54203
  Stored in directory: /private/var/folders/_h/t3wvkks5643fxnv07_kx9cx8000zpt/T/pip-ephem-wheel-cache-e2in5dui/wheels/dd/f6/e5/9a3d70fd7e89a7d0485da7c363747fffce8f6596dab2b28068
Successfully built pcmdi-metrics
Installing collected packages: pcmdi-metrics
Successfully installed pcmdi-metrics-2.5.1

[xylar]

This should probably close #894

[tomvothecoder]

Thanks for the feedback @xylar, I followed your instructions more closely this time.
Also thanks for pointing out that @lee1043 opened #894 which is a duplicate of this one.

This one includes an additional fix to make pre-commit work, so we can close #894 if preferred.

[lee1043]

Thank you @tomvothecoder and @xylar for your help on this!