Integrate gitlab-ci/fix-remote-name-on-retrigger and 1 more

Commit: seco-ne/yocto/infrastructure/gitlab-ci@c917791b

Fix remote name on retrigger stage

--

Commit: seco-ne/yocto/infrastructure/gitlab-ci@1ba52853

Move repositories to git.seco.com

Rename variable JENKINSGUF_SSH_PRIVATE_KEY / SSH_PRIVATE_KEY to GITLAB_PRIVATE_KEY on this occasion, because it contains a private key that was generated exclusively for this use case. The according public key has been added as a deploy key in GitLab to all repositories that this repository needs access to.

Add more detailed documentation concerning this configurationdirectly in the gitlab-ci files.