Provide intermediate version tags to Docker Hub

This issue has been migrated from [#9589](https://github.com/matrix-org/synapse/issues/9589).

---

The tags currently provided are either `latest` or the specific build version.
It would be nice to provide the intermediate version segments as well.
For example:
A build of version `v1.29.1` would provide the following images to Docker Hub:
```text
latest
v1.29.1
v1.29
v1
```

This allows users to lock their configurations to a specific major version or intermediate version.
Especially helpful in combination with update mechanisms so a new major version is not automatically rolled out when/if `latest` updates with non-backwards compatible changes.

As an example, see how some major vendors configured their tags:
- [nginx](https://hub.docker.com/_/nginx)
- [mysql](https://hub.docker.com/_/mysql)
- [postgres](https://hub.docker.com/_/postgres)