[discussion] Add Window Splitter component?

*⚠️ Info: This issue is for product research, to gather community input. In this [base-ui repo](https://github.com/mui/base-ui) we are, currently, focused on the core set of components needed to create a great design system, so the probability we build this in this repo is very low.*

## Summary

## Examples in other libraries

- https://github.com/bvaughn/react-resizable-panels
- https://github.com/mathuo/dockview
- https://github.com/caplin/FlexLayout
- https://github.com/ticlo/rc-dock
- https://github.com/jupyterlab/lumino
- https://github.com/golden-layout/golden-layout
- https://github.com/nomcopter/react-mosaic
- https://github.com/johnwalley/allotmenthttps://github.com/gridstack/gridstack.js

*([internal benchmark](https://www.notion.so/mui-org/x-Window-splitter-component-cf1bd8b84b85429b8cc2fcb860d617dd))*

## Motivation

TBD

- User requests:
- https://x.com/dawi80/status/2041491113626787970
- UI library requests:
- https://github.com/shadcn-ui/ui/issues?q=is%3Aissue%20state%3Aopen%20Resizable
- https://github.com/mui/mui-x/issues/512

One can also argue that #4788 is a more complex version of this component.