NegLogParameterPriors does not evaluate prior density at fixed params

[arrjon]

Based on #1412

Making the NegLogParameterPriors aware of fixed parameters. The density is not evaluted for those. Moreover, the petab importet is updated to indicate the fixed parameters while creating the prior.

Question: should this argument stay optional? If priors are not given for fixed parameters, no problem would occure. The problem only occurs when priors are given and parameters fixed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 83.90%. Comparing base (2250dbc) to head (b178863).

Files	Patch %	Lines
.../objective/roadrunner/petab_importer_roadrunner.py	50.00%	2 Missing :warning:
pypesto/petab/importer.py	50.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #1413 +/- ## =========================================== - Coverage 83.92% 83.90% -0.03% =========================================== Files 160 160 Lines 13061 13067 +6 =========================================== + Hits 10962 10964 +2 - Misses 2099 2103 +4 ```

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[dilpath]

Thanks! Sorry for the mask suggestion, I wasn't familiar with the code

[arrjon]

Also not entirely sure whether it is relevant, but the problem has a function fix_parameters, for this it should be accounted as well? 🤔

That is relevant, but the function calls normalize, which in turn calls update_from_problem, so no need to add in fix_parameters.

[arrjon]

After discussing this issue in #1412, we will not make the prior aware of fixed parameters. Instead, users should specifiy priors correctly in the PEtab problem. In this way, we will allow maximum flexibility.