Use docker images built in previous stages
Apologies if there is already an issue for this request; I was unable to find it.
We should be able to set the Docker image that is used for the build dynamically so we can build a docker image in one stage and run all later builds using that image. Ideally, the feature would support completely dynamic image names so that images that weren't necessarily built using a CI job can be used (e.g. reference an image that has no direct relation to the commit or pipeline ID).
At the very least, variables should be useable in the image
option on both the global and job level.