applet: Toggle Bluetooth status on middle-click
BUG: 427816 FIXED-IN: 5.24
Code-wise this is slightly non-ideal since it relies on implicit parentage (CompactRepresentation.qmluses a function that lives in BluetoothApplet.qml, which is its ultimate parent), but this is unavoidable because the applet is already relying on this in a ton of places and a wider refactor of that would be a separate project.