windsock-cloud-docker: cleanup running processes when killed

[rukai]

Refactor windsock-cloud-docker so that it cleans up the in progress cargo command.
Its very common to want to kill cargo while its building if I change my mind.
Currently when I do that to windsock-cloud-docker it leaves a stray cargo process running in the background which will:

• block new cargo compilations until the original cargo finishes compiling
• eventually proceed to spin up AWS resources, without me being aware

This is quite problematic.

To fix this I:

1. refactored windsock-cloud-docker to be async
2. split all the logic between a Container::new() and Container::run_windsock methods
3. then used tokio::select to allow sigint (ctrl-c) to terminate an in progress run + run cleanup code.
   Doing this without async is quite difficult as we would need to refactor commands to be nonblocking, better to just go async at that point than manually dealing with non blocking commands.

The actual logic of setting up the container and running windsock remains the same, its just all asyncified.

This PR also removes an unrelated stray TODO which had already been addressed in a previous PR.