Allow reordering search all results

[mrclay]

Simple: After $types = get_registered_entity_types(); run $types through a plugin hook so plugins can reorder the array.

Better: Render each section into an array with keys like type:subtype and pass that through a hook.

[Srokap]

Maybe just run it through menu system? It would allow to tap to menu's plugin hook for reordering.

Edit: I misunderstood general idea. Was thinking about menu items in sidebar. Plugin hook sounds fine.

[mrclay]

PR #6350