Modernize setup and CI

[dzalkind]

Description and Purpose

Collect changes, update docs, fix remaining bugs before 2.9.0.

Type of change

What types of change is it?
Select the appropriate type(s) that describe this PR

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

TODO Items General:

• Add example/test for new feature
• Update registry
• Run testing

TODO Items API Change:

• Update docs with API change
• Run update_rosco_discons.py in Test_Cases/
• Update DISCON schema

Github issues addressed, if one exists

Examples/Testing, if applicable