[release tool]: merge staging pull requests through the tool itself

Currently it is unclear what should be used to merge staging pull requests. We should just let the release tool merge the PR as it knows exactly where the PR should go into. The merge tool would rely on target labels which might not work temporarily e.g. when branching-off a feature freeze.

We should either merge automatically once the PR is approved + checks are passing, or we just add a double-prompt that can be submitted to manually start the merging (useful in case the PR checks are not significant as in COMP and FW - though worth noting that this could be done through a configuration as well in `.ng-dev`.)

The cherry-pick PRs should be merged automatically based on our discussion

Commencez par localiser le flux de merge des pull requests de staging de l’outil de release et examiner la configuration `.ng-dev` mentionnée dans l’issue. Comparez le merge automatique avec la double invite proposée et les options de configuration, y compris le comportement de cherry-pick indiqué. Le travail est considéré comme terminé lorsque la politique de merge est décidée et implémentée pour les cas de staging et de cherry-pick décrits.

Rédigé par le modèle d'indexation à partir du texte de l'issue.