Fix `return_dict` when an `AmiciObjective` is inside `AggregatedObjective`

[dilpath]

AmiciObjective previously returned all AMICI RData information when return_dict=True. However, this was handled via __call__. If the PEtab problem has a prior, then an AggregatedObjective is created, with an AmiciObjective and the prior inside. The AggregatedObjective calls call_unprocessed of each internal objective, skipping AmiciObjective.__call__ and hence one would see something like:

# call AggregatedObjective
>>> result = objective(x, return_dict=True)
>>> result['rdatas'][0].y is None
True
>>> result = objective(x, return_dict=True, amici_reporting=amici.RDataReporting.full)
>>> result['rdatas'][0].y is None
False

This PR changes the above to

>>> result = objective(x, return_dict=True)
>>> result['rdatas'][0].y is None
False

i.e., rdatas are now "full" and e.g. plotting is now possible.

An alternative fix would be to always pass return_dict to call_unprocessed. This would be fine for me, but might break someone's custom objective.

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Attention: Patch coverage is 93.75000% with 1 line in your changes missing coverage. Please review.

Project coverage is 83.35%. Comparing base (5a8e014) to head (b9ec235).

Files	Patch %	Lines
pypesto/objective/aggregated.py	83.33%	1 Missing :warning:

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```diff @@ Coverage Diff @@ ## develop #1424 +/- ## =========================================== + Coverage 83.33% 83.35% +0.01% =========================================== Files 161 161 Lines 13226 13235 +9 =========================================== + Hits 11022 11032 +10 + Misses 2204 2203 -1 ```

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[dweindl]

An alternative fix would be to always pass return_dict to call_unprocessed. This would be fine for me, but might break someone's custom objective.

I think this would make sense. Your current implementation would already enable issuing a DeprecationWarning and updating things accordingly.

[dilpath]

An alternative fix would be to always pass return_dict to call_unprocessed. This would be fine for me, but might break someone's custom objective.

I think this would make sense. Your current implementation would already enable issuing a DeprecationWarning and updating things accordingly.

Thanks, I decided to simply switch to it by default now, with a DeprecationWarning.