Add continuous integration for gitlab-ci

Created by: yanicasa

new CI for gitlab massively generic to allow each group to be able to use it directly without modifications in the CI source code regardless of their runtime environment.

Adaptations to the environment are done only in the settings of the projects. (paths of tools, version of tools, urls of repositories to use...)

The CI launch 2 downstream pipelines:

CVA6 : the CI previously describes in .gitlab-ci.yml (not used anymore I understand?)
CORE-V-VERIF: a new CI based on core-v-verif environment

trial in test branch "feature/gitlab-ci" see : #797