Docker tagging

[timakro]

Main intention same as #52:

Currently, the latest tag is always added to the images from the repositories default branch.
With this change, the latest tag will only be updated when pushing a git tag matching the semantic versioning scheme.

This PR implements it differently, instead of using type=match it uses flavor: latest=auto. This aligns with the examples in the docker/metadata-action readme and seems to be the intended way of controlling the "latest" tag

Details

Updated the tagging rules to be roughly equivalent to the semver example from the docker/metadata-action readme here.

Also disabled <major> tagging when major is 0 as suggested in docker/metadata-action readme.

Also removed suffix=${{ inputs.image-tag-suffix }}pr- as this was bogus anyways and most likely not needed as global prefix and suffix should apply always.

Also removed a step that I believe was unused (see commit message of first commit)