Make the entire code base PEP8 compliant.

[carldlaird]

[mrmundt]

IDAES recently implemented the usage of black to enforce PEP8 compliance; in interest of compatibility, I would like to implement the same. I intend to run black on the entire codebase after the following are merged:

• Update model viewer to support PySide6 and display units and domain. #2689
• Mindtpy rewrite #2654
• Add support for Xpress callbacks in Pyomo. #2648
• Add Pyomo.DOE to contrib  #2294

[jsiirola]

I have one more big PR coming that it would be nice to wait a bit and not conflict. I am still working to get a couple tests passing and then can put up a WIP PR so that you can (hopefully) avoid those files while you start applying black.

Should we do black in chunks to keep the PR process simpler, or do it in one big chunk so that we only need to have a small number of revs in the .git-blame-ignore-revs file (see here)

[mrmundt]

I intend to do the black application in chunks so as to not make it a reviewing nightmare.

Also, for posterity, I intend to run this command: black -S <path> <- The -S skips string normalization.