Get component versions for cng tagging

Gathers the same information we use to update omnibus and formats the data in a way that is acceptable to CNG. Reference the following file: https://gitlab.com/gitlab-org/build/CNG/blob/master/ci_files/variables.yml

• Adds ability to gather and send a commit similar to how ominbus works, but formatted slightly different due to the inconsistency between omnibus and CNG.
  • Plucks mailroom version from a Gemfile
  • Changes the GITALY_SERVER_VERSION to only GITALY_VERSION
  • changes VERSION to the three varieties of GITLAB specified for CNG building
  • Ensures we maintain the v in front of our tags, and no v when not using a tag in the correct locations
• tags CNG which will trigger a build

Addresses: gitlab-com/gl-infra/delivery#577 (closed)