Destroy request is not specified for foreign toplevel manager and it
does not prevent the compositor from sending more events.
Libwayland would ignore events to a destroyed objects, but that could
indirectly cause a gap in the sequence of new object ids and trigger
error condition in the library.
With this commit waybar sends a `stop` request to notify the compositor
about the destruction of a toplevel manager. That fixes abnormal
termination of the bar with following errors:
```
(waybar:11791): Gdk-DEBUG: 20:04:19.778: not a valid new object id (4278190088), message toplevel(n)
Gdk-Message: 20:04:19.778: Error reading events from display: Invalid argument
```
b79301a5bd