Push runner-helper image to Dockerhub during deploy stage

This MR adds support for pushing both arm and x86_64 images for the runner-helper to Dockerhub. This was created to open discussion on how to deal with runner-helper when running on remote machines (aka on a Kubernetes cluster, where docker import is not available).

It pushes an arm and x86_64 image with the commit hash of the runner at that point in time in order to facilitate the runner versioning the helper image.

As a result of this MR, docker becomes required during the deploy stage. This is so that any version of the runner is able to use it's own build hash to pull a versioned copy of the runner-helper image. The build stage still does not enforce the use of Docker.