Support multiple alpine base images

[wholtz]

I just added alpine-3.18 as a base image (frolvlad/alpine-glibc:alpine-3.18 to be exact). I failed to notice that I had not configured image tagging that will allow us to have more than one alpine image per micromamba version (ie, we have alpine, not alpine3.17 and alpine3.18). I will look into supporting multiple alpine images.

Currently for our non-alpine images, there is a distribution release identifier tag (we have a bookworm tag, not a debian tag). But we don't have this for alpine. Should we deprecate the alpine tag and move to alpine3.18? That would seem to be the most consistent and it allows me to add newly released base images (ie, alpine3.19) without having to wait for a minor version release of micromamba (so that we don't end up with what I accidentally did today, where a tag alpine can change from one distro release to another). The other option would be to:

1. keep alpine as a tag
2. add alpine3.17 and alpine3.18 as tags
3. add release independent distro tags for debian, ubuntu, and ubuntu-cuda
4. and then only add base images on a minor version release of micromamba

I'm inclined to go with the former option (deprecate alpine).