Feature request: Rework `split view` and `resizable panel`

[akphi]

Personally, this has always been something I care about deeply because this is a fun and quite challenging problem; also, react support for this seems surprisingly lacking, popular libraries like react-split-pane are no longer maintained, and the alternative that we picked which is react-reflex has their own outstanding problems:

• Is there a way to completely hide minimized panel? leefsmp/Re-Flex#146
• Bug: programmatically set size results in different flexGrow leefsmp/Re-Flex#147

Implementation Plan

We don't really have a good idea of where to start, but it seems like if we can learn from what vscode does with sash and splitview that would be great, flex-based solutions like react-reflex seems to have their own quirks, so maybe a pixel-perfect approach is something we should be looking at.

See https://github.com/microsoft/vscode/tree/main/src/vs/base/browser/ui/splitview

• Checkout react-resizable-panels
• Check if we still need the hack in Horizontal container splitter drag not working on page load leefsmp/Re-Flex#27

Other references

We are pretty much enraptured by the way vscode does this, but it's very low-level and could take time to learn what they did. There are higher-level solution:

• Storybook: using react-dragable - https://github.com/storybookjs/storybook/blob/7064642e1aee7786c77fe735c064c0c29dbcee01/lib/ui/src/components/layout/container.tsx