Remove BaseTabs

[bennypowers]

Affects <rh-tab>

See also #2577
See also #

### Tasks
- [ ] https://github.com/patternfly/patternfly-elements/pull/2577
- [ ] https://github.com/patternfly/patternfly-elements/issues/2575

[bennypowers]

It's worth considering if we should shipg a separate AccordionController, or maybe modify TabsController to suit accordion as well,

or maybe have TabsController AND AccordionController, but have them both share code via a base class or a 3rd controller (remember: controllers are able to add other controllers)

[bennypowers]

Closed by #2745