Ensure Ansible installed with Python3.9

[brucellino]

This fixes mmul-it/kpa#5

This PR contains:

1. Packer template (written to correspond to Dockerfile) -- however ensures pip3 with python3.9 is invoked when installing ansible
2. pre-commit hooks and sundry

The packer template diverges from the Dockerfile in that it makes greater use of declarative versions -- e.g. the requirements.txt file for the image, etc.

[brucellino]

@rascasoft can you review this please? It contains updates to the pipeline so that you can build the image with packer (nothing has been removed.)

The pipeline is also triggered on PRs now, instead of only main branch commits -- no pushes occur on that yet to the docker registry.

When this is merged, we can deal with the semantic release bits

[rascasoft]

@brucellino I've implemented a way of managing releases that should fit in what we have right now, without the need of integrating anything else.
It is all part of the v1.0.0, specifically in the d1e80a7 commit which takes the branch and generate the tags.
I would like to test this infrastructure and see if it fits our need, so lets put this in the fridge for the moment.