replace usage of @cascades in favor a context implementation in `pf-tabs`

> [bennypowers](https://github.com/bennypowers) [5 hours ago](https://github.com/patternfly/patternfly-elements/pull/2577#discussion_r1413636838)
If there's any way to get rid of these @cascades decorators (maybe a context?) it would help simplify things quite a bit IMO
>
> can be a followup

Look at replacing in favor of context.