Add molecule tests to collection

[widhalmt]

Fixes #41

[widhalmt]

Some of the checks won't run locally as easy as they do in GitHub actions. So this might get a long trail of trial&error commits before it's ready to merge.

[widhalmt]

@lbetz / @mkayontour please tell me what you think of the code.

Please don't just merge it now. We'll need to make very sure to have the commits squashed during merging and I want to review all the commit messages. There's a lot in them that was just used "under way" but doesn't bring any benefit when we have it in the history of main.

[mkayontour]

The CI Status doesn't work, this generic one does work.
https://github.com/Icinga/ansible-collection-icinga/actions/workflows/molecule.yml/badge.svg

[widhalmt]

The other badge should work, once it's merged. The pipelines the link is referring to, does not yet exist. But we can always change it to the more generic one to be safe. I'll change it.

[mkayontour]

Everything looks good to me, for the basics this is enough. I'll add a few more cases and scenarios after the merge is done!

The install.rst is something I would remove - because it could be distracting but let me hear what you think.
Thanks buddy :)

[widhalmt]

Thanks for your feedback, @mkayontour . I tried to apply the changes you requested. Could you have another look?

[widhalmt]

Talked to @lbetz . He's swamped with other tasks now but he's ok, with me merging. So: merging. Yay.