chore: new Poetry-only Dockerfile

[gruzewski]

New Poetry-only Dockerfile

Adds a new Dockerfile that installs all dependencies using poetry. The idea is to build it alongside the existing image and test it extensively.

Testing:
I built the new Dockerfile and re-compiled examples/kubernetes with it.

[uberspot]

Nice, should we also modify the github action to build this and publish other tags with it? Or is that already covered?

[gruzewski]

Nice, should we also modify the github action to build this and publish other tags with it? Or is that already covered?

I was planning to do that in a separate PR. But I am happy to do it here.