Menu item to pull container images

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

I am trying to pull container images, but I have to do this in the CLI.

### Describe the solution you'd like

I would like an option in the web UI to do this.

### Additional context

I *could* change the pull policy, but this presents a problem for some private repos. For example, ACR tokens time out in less than a day (no idea if this can be changed - doesn't matter: most users will experience this by default) meaning that an "always" pull policy will spuriously fail (even if the container has no changes) multiple times a day and require the developer to use `az acr login` from the CLI anyway.

The better option would be to allow the developer to initiate the pull from the UI.

I would PR this myself, but DCP is undocumented and closed source.

Restarting the container issue is another discussion entirely and probably shouldn't bog this one down. It isn't too much to ask to click "pull" and then "restart".