Simplify docker image rules
This is a part of !3605 (closed), which was too big to review. This MR simplifies the rules for docker image related jobs.
-
.rules_scheduled_manual
-> Only used for docker images, so name it.rules_docker_images
-
.rules_docker_image_tests
-> We reuse the same rules for several docker image test jobs, so let's add a SSoT for that.
To be merged after !3609 (merged)
Related issues
- Related to #1324 (closed)
- Related to gitlab#389812 (closed)