Don't create DAG cycles via automatically added functions

[MImmesberger]

What problem do you want to solve?

Closes #757

In fact, any occurences of automatically created cycles reported in #757 have already been solved via the namespaces structure.

In ALG2 we have

@policy_function(start_date="2005-01-01")
def wohnfläche(
    wohnen__wohnfläche_hh: float,
    anzahl_personen_hh: int,
) -> float:
    """Share of household's dwelling size attributed to a single person."""
    return wohnen__wohnfläche_hh / anzahl_personen_hh

So we don't create a cycle anymore as we have wohnen__wohnfläche -> wohnen__wohnfläche_hh but wohnen__wohnfläche_hh -> arbeitslosengeld_2__wohnfläche.

Still, thanks to the work done by Lars in the past, a general TTSIM solution was easy to implement because it just copies the logic done for time-conversion functions.

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...dag_elements/test_automatically_added_functions.py	80.00%	2 Missing ⚠️

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[hmgaudecker]

Very nice, thank you!