Add tabbed inspector UI and attributes

[MaykerStudio]

Introduce tabbed inspector support: add runtime attributes (BeginTabGroupAttribute, TabAttribute, EndTabGroupAttribute and TabGroupVisual) and an editor drawer (BeginTabGroupAttributeDrawer) with responsive, styled tab rendering (Default/Flat/Segmented), tab state management and type/field discovery caching. Register new drawers in Editor Toolbox settings and add TabAttributeDrawer/EndTabGroup handling. Update example scene and SampleBehaviour4 to demonstrate tab groups and polish formatting. Also include small EditorUserSettings tweaks. Most of the code was writen by LLM but the general concept and optimizations was manually writen.

[arimger]

Hi! Thank you very much for this PR. I really like the general idea and some solutions, but I can't merge it into the master branch in its current state. If you want, we can go with the classic review process, or you can change the target branch to develop, and I will handle it by myself. 2nd option is a bit more convenient for me.

In general, I would like to change coding convention-related things, such as formatting, file structure, and member names, to match other scripts in the package. Additionally, it would be nice to avoid some allocations (e.g., right now you are creating a few Lists), and I can see some potential improvements to static utility classes: TabDiscovery and TabState.

[MaykerStudio]

• No worries. Feel free to change anything, cheers.

[FredTA]

This looks cool! Would be interested in using this :)

[MaykerStudio]

Sorry, I've set the wrong branch. Fixed!