Documentation about `ENTRYPOINT` and `COMMAND` override options in gitlab-ci.yml is confusing

• We don't have the descriptions about services:name, services:alias, services:entrypoint, services:command, image:name, image:entrypoint in gitlab-ci.yml keyword list => https://docs.gitlab.com/ee/ci/yaml/
• We have a dedicated section in https://docs.gitlab.com/ee/ci/docker/using_docker_images.html#define-image-and-services-from-gitlab-ci-yml, but it seems not connected to gitlab-ci.yml section
• The doc section in runner side https://docs.gitlab.com/runner/executors/docker.html#the-entrypoint still recommends an old solution.

/cc @axil