Device agent should be notifed if deleted in forge app

### Current Behavior

The device agent will continue to try and connect to the Forge platform if run after it has been deleted

### Expected Behavior

The forge app should send a message to the device agent when it is deleted so it stops the flow and stops trying to connect.

### Steps To Reproduce

Create device
assign to instance
assign snapshot
delete device

### Environment

- FlowForge version: 1.10.0
- Node.js version: 16.x
- npm version: 8,x
- Platform/OS: any
- Browser: any