Create non-Alpine, Debian/Ubuntu images

Alpine's own peculiarities (particularly its use of musl instead of glibc) sometimes causes problems that are hard to track down (see eg https://github.com/amercader/ckanext-embeddings/issues/4). Alpine was used as a base image originally to reduce the image size, but given that CKAN itself is not a micro-service where this might be important when deploying, I think most users would prefer the predictability and convenience of working in a Debian/Ubuntu based image.

| Image | Size (linux/amd64) |
| --- | --- |
| `alpine:3.19` | 3.25 Mb |
| `debian:12-slim` | 27.77 Mb |
| `debian:12` | 47.26 Mb |
| `ubuntu:22.04` | 28.17 Mb |

My personal preference is to use the Ubuntu one as this aligns with what we support in the Deb packages and the source installs, but happy to hear other thoughts.

We should tag these images differently, ev `ckan:2.10-ubuntu`

Note that the Keitaro folks have been maintaining Ubuntu based images for a while: https://github.com/keitaroinc/docker-ckan