Add tests for pyiron-installer

[jan-janssen]

At least for Linux it should be possible to automatically install conda from the installer which was created and then run a couple of tests just to see if the typical workflows are working.

[jan-janssen]

A different approach to address this challenge is using the same environment for both the docker container and the installer. https://github.com/jan-janssen/shared-conda-environment follows this approach of building the same environment in both the docker container and the installer.