Update tags to use only runnermia stable for dind jobs (other custom runners doesn't work well with dind)

(they are renamed, and are not actually required)

Force l'utilisation de la version docker:20.10.20 pour éviter les problème dind avec les runners (voir issue gitlab-ci-templates#7)

+ active docker build cache

(remove first /)

(some related to new projet urep/dev_utils/gitlab-ci-templates)