Use system Puppet in CI

[ekohl]

This uses the official Puppet AIO packages, which is also what we use in production. This makes the tests more realistic.

Currently just testing out if this even works.

[ekohl]

I think librarian isn't friendly with the AIO Puppet: cannot load such file -- concurrent. I suspect it doesn't properly purge the bundler environment variables (like we do in Kafo).

[ekohl]

As I wrote somewhere else: I'm leaning to adding a step that builds the modules as separate from the others. Then store it in a cache and reuse it in the other axes.