Function deltachat::imex::transfer::spawn_progress_proxy

fn spawn_progress_proxy(context: Context, rx: Receiver<u16>)

Spawns a task proxying progress events.

This spawns a tokio task which receives events from the [ProgressEmitter] and sends them to the context. The task finishes when the emitter is dropped.

This could be done directly in the emitter by making it less generic.