Cleanup the multi-type context menu item

[ardcore]

This fixes #7816 and simplifies the logic of context menu item by making a distinction between the submenu collection and the structure of a multi-type item.

By creating a new collection (items), we're able to treat the multi-item as a normal item (sharing all it's behaviours -- lack of them was the precise cause of #7816 ). This also solves some other, probably unfilled issues (i.e, it wasn't possible to focus the multi-type item using keyboard[1]), and makes it possible to define multi-type items with submenus, if needed.

[1] - While this PR makes it possible to select the multi-item, keyboard navigation still won't work inside it. I believe this should be discussed in another issue.

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Test Plan:

See #7816

[cndouglas]

Works for me.

[bsclifton]

Works great 😄

lint passes, unit tests pass, and webdrivers tests using npm run test -- --grep="hamburger" pass

[bsclifton]

@ardcore congrats on your 1st commit landing in Brave 🎉 😄 (hopefully of many more!). If you need help with anything in the future, please let me know