E2E Test of Deployer

We want users to upgrade to the latest GRIT version regularly and confidently. This allows improvements and bug fixes to roll out quickly and simplifies the space of runner configurations GitLab teams must support. In order to build and maintain that confidence, we must test not only releases, but upgrades from previous releases.

We must have an automated test run before minor version release (it's okay not to run this on every MR) which asserts the release can safely be applied on top of the last N (say 3) released version. And conversely the candidate release can safely be downgraded to the last N versions. This ensures upgrades aren't a one-way-door which should instead be released with a major version bump.