Move the helm changelog compilation before the version bump
We also add the new changelog before that
This is previously where the changelog manager was running, moving it to be after the version bump caused issues where we failed to swap to the stable branch again after the changelog compilation, and we were also tagging the changelog commit, which included ci-skip. So release piplelines were not working
Fixes: https://gitlab.com/charts/gitlab/issues/772 Fixes: https://gitlab.com/charts/gitlab/issues/773