Consider switching to CutefishOS Dock

Consider switching to [CutefishOS Dock](https://github.com/cutefishos/dock)

Advantages:
* Works correctly with multi-monitor setups
* Applications in the Dock can be ordererd by drag-and-drop
* Supposedly can empty the Trash (could not confirm it working on helloSystem)
* Can be put to the left side of the screen rather than to the bottom with `Direction=0`

```
[General]
Direction=0
IconSize=48
RoundedWindow=false
Style=0
Visibility=0
```

But:
* Introduces a dependency on https://github.com/cutefishos/fishui (can it be made a compile-time option?)
* Application Bundle support would need to be ported over (ideally upstreamed)
* It seems to become very CutefishOS centric, e.g., ` QDBusInterface iface("com.cutefish.Session", "/Session", "com.cutefish.Session", QDBusConnection::sessionBus());` - what is this for?
* Pinning menu item missing?
* `RoundedWindow=false` has no effect
* Opening the Trash does not work anymore

Blocked by:
https://github.com/cutefishos/dock/issues/10