This diff splits miniooni's implementation in smaller and more
easily tractable blocks ahead of future refactoring.
I'm trying to make `miniooni oonirun -i URL` as possible as
`miniooni -i URL oonirun`, because users typically expect this
kind of flexibity from modern Unix commands.
Part of https://github.com/ooni/probe/issues/2184
We used to have an external package called libminiooni so that
third parties could use it. We wrote this such that we could
support github.com/bassosimone/aladdin.
That was actually a not-so-good idea because it added to the APIs
we needed to maintain.
Since the merge of engine into cli, such an API is not public
anymore and aladdin has been deprecated and archived.
Therefore, we can now cleanup the situation and merge libminiooni
into miniooni again, thus making the codebase more local.
This cleanup has been identified while working on
https://github.com/ooni/probe/issues/1299.
