feat: Add NcAppNavigationList

[Pytal]

☑️ Resolves

• There are cases where having multiple uls inside NcAppNavigation makes sense i.e. using NcAppNavigationCaption as a label for the next ul
• We add a new NcAppNavigationList component to be used in the default slot of NcAppNavigation
• Allow using NcAppNavigationCaption as a heading with a prop

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 3️⃣ Backport to next requested with a Vue 3 upgrade

[ShGKme]

Is ul.app-navigation__list different from NcAppNavigationList?

[susnux]

Also stumbled over this one, could we not just use NcAppNavigationList here instead?

[Pytal]

Is ul.app-navigation__list different from NcAppNavigationList?

Yes slightly. The difference is ul.app_navigation__list always fills the height that is not already taken up by its siblings inside nav.app-navigation__content but when we have separate lists inside the nav we want don't want that e.g.

so we adjust the styles in NcAppNavigationList to keep the styling we want:

The .app_navigation__list styles also target .app_navigation__content > ul which we should keep to not break anything, so we also increase the specificity to have the styles apply correctly

[JuliaKirschenheuter]

great refactoring work!

[Pytal]

/backport to next