[Spike] Reduce or eliminate unnecessary portalling in EUI Components

## Summary

Put a more tangible plan around https://github.com/elastic/eui/issues/9503.
- What is an easy first step we could take? (High Value, Low Effort)
- What are the technical approaches we could take?
- How much work would it be to address this across EUI in it's entirety?

## Definition of Done
- [ ] update https://github.com/elastic/eui/issues/9503 with your findings
- [ ] (ideally) create at least 1 task tangible task that would could be a first step to improvement. It should include a time estimate so that we can plan it.