Add support for menu subsubitems

[jomunker]

depends on #1233

This PR adds support for menu subsubitems (third level items).

Screenshots

[jomunker]

• add changeset

[johnnyomair]

I'll review this once #1233 has been merged. Setting as draft for now.

[johnnyomair]

@jomunker the base PR has been merged, please update this branch and solve conflicts so we can review it again, thanks!

[jamesricky]

Could you please add an example of this feature to the dev-stories?
Either in a new story or maybe in the existing menu-story: packages/admin/admin-stories/src/admin/mui/Menu.tsx

This would be very helpful for review and for future changes/debugging of this feature.

[jamesricky]

 @jomunker the implementation seems to differ from the design:

• The selected sub-sub items should not have a blue background but the text and the border on the left should be blue instead.
• The left border of the last item should extend all the way to the bottom of the item, like the border on the first item extends all the way to the top.

Are these things already implemented in one of the follow-up PRs?
Or do I maybe have an outdated design?

Current implementation	Design

[jomunker]

@jomunker the implementation seems to differ from the design:

• The selected sub-sub items should not have a blue background but the text and the border on the left should be blue instead.
• The left border of the last item should extend all the way to the bottom of the item, like the border on the first item extends all the way to the top.

Are these things already implemented in one of the follow-up PRs? Or do I maybe have an outdated design?

Current implementation Design

Seems like i fixed the design in the follow up PR. See the following screen recording. Sorry for the confusion with the follow up PRs.

Screen.Recording.2024-02-29.at.10.21.42.mov

[jamesricky]

Seems like i fixed the design in the follow up PR. See the following screen recording.

The bottom part of the border on the last item is still missing in the video.
Can you please add that? In a follow-up PR is fine.