[UX] Admin bar search: Make certain search results distinct by prefixing their immediate parent item.

Follow-up for #525

As mentioned in that issue:

...even if we implemented the above, we'd be 90% there. You see there would be these menu items:

Structure -> Taxonomy -> Tags -> List terms Structure -> Taxonomy -> Categories -> List terms Structure -> Taxonomy -> Another vocabulary -> List terms

...as well as these ones:

Structure -> Menus -> Account menu -> List links Structure -> Menus -> Administration menu -> List links Structure -> Menus -> Primary navigation -> List links Structure -> Menus -> Another menu -> List links

So if one was to enter the search term "list" in the admin bar search field, they'd get this (@TODO: add screenshot):

... Structure: List terms Structure: List terms Structure: List terms ... Structure: List links Structure: List links Structure: List links Structure: List links ...

This is way better than plain plain "Structure: List" for all these results, but still... can we (I don't know if this is possible) have it so that the search results (just the search results - not the menu items themselves) are like so instead:

... Structure: List Tags terms Structure: List Categories terms Structure: List Another vocabulary terms ... Structure: List Account menu links Structure: List Administration menu links Structure: List Primary navigation links Structure: List Another menu links ...

...or like so perhaps (prefix the "immediate" parent menu item along with the top-most parent item):

... Structure: Tags: List terms Structure: Categories: List terms Structure: Another vocabulary: List terms ... Structure: Account menu: List links Structure: Administration menu: List links Structure: Primary navigation: List links Structure: Another menu: List links ...