Change release pattern

[AndyRae]

We would like to change the current release workflow slightly, uncouple our instances of Carrot, add registries, and incorporate more robust semantic versioning.

Objectives:

• Any merge to main should increase the version number and publish a new release.
• Publishing a release should also publish the 3 (api, frontend, workers) to the Github docker registry. (Container Registries #863)
• We then publish these images to our dev/test instance on every release (pull them to our registry, and retarget infrastructure in workflow).
• We then (manually) run a workflow to publish to carrot.ac.uk when we are happy with a release (retarget infrastructure).