Drag & drop for move: breadcrumbs as drop target

[kulmann]

User story

As a mouse user I want to move selected files via drag & drop to a parent location, so that I can not only move down the folder tree, but also up.

Acceptance criteria

• accept parent breadcrumb items (obviously not the current folder / last breadcrumb item) as a drop target in drag & drop mode.
• highlight the breadcrumb items in the same way the file rows in the files table get highlighted after Drag & Drop for move: highlight drop target #5705 is done
• don't copy the code. find a generic solution which can be used for dropping in file list and in breadcrumbs (which don't live in the view, but in the AppBar). idea: implement as a service.

[kulmann]

Closing in favour of more detailed #7454