Menu: Wrap menu items in a <div>

This avoids styling issues where ui-state-focus rules apply to submenus.

Fixes #10162
Closes gh-1342
Autocomplete: Re-add wrappers to menu items
Selectmenu: Re-add wrappers to menu items
Revert "Selectmenu: Remove broken tabindex code"

This reverts commit 1fb08790a6cae0ac861df0373a303d72ed0e8d71.
Selectmenu: Use native element's tabindex

Fixes #10665
Closes gh-1345