Pull docker images reporting

[tarnas14]

refactor backend docker image management

AC:

1. extend image_list to include information if there is a newer version available on docker hub
   
2. expose a tauri command to pull a specific image instead of all images
3. expose an event stream of image pull operations, tari://pull_image_progress, (both pull_image and pull_images) , which would push events like

{
  dockerImage: "<image_name>", // full name of docker image so we can assign state to it
  status: "pulling", // DockerImagePullStatus
  progress: 20, // progress in %
  error: "error message or null" // if there is an error message, we show it to the user
}

enum DockerImagePullStatus {
  Waiting = 'waiting',
  Pulling = 'pulling',
  Ready = 'ready',
}

NOTE: right now an event stream of verbatim docker strings is pushed, we can either leave it like this and show to the user or parse and stream that
4. the above commands need to accept dockerRegistry and dockerTag as parameters, as it is configurable on launchpad

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statuses (up_to_date, waiting, fs_layer, pulling)