TPv2 Abstract Table Class

[ocket8888]

This PR adds a new abstract class that encompasses the basic, common behavior of generic TPv2 tables. It also converts the Cache Groups, Regions, and Divisions tables to use it, to demonstrate its use.

The idea here is to ease creation of a common type of component. It's possible that instead we'd want to just make the generic table itself abstract and collapse the two. Idk. Really just interested in feedback at this point.

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Which Traffic Control components are affected by this PR?

• Traffic Portal (experimental v2)

What is the best way to verify this PR?

Don't. I'll bother writing tests if people think this is even a good idea.

PR submission checklist

• [ ] This PR has tests
• [x] This PR has documentation
• [x] This PR doesn't need a CHANGELOG.md entry
• [x] This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY