Refactors BaseCost.evaluate/S1 into BaseCost.compute

[BradyPlanden]

Description

This PR refactors BaseCost.evaluate/S1 & BaseCost._evaluate/S1 into BaseCost.__call__ and BaseCost.compute. BaseCost.compute directly acts on the predictions, while BaseCost.__call__ calls BaseProblem.evaluate/S1 before BaseCost.compute. Fully separates __call__ and compute for FittingCosts, Likelihoods. This PR also has bugfixes to GaussianLogLikelihood calculation.

Issue reference

Fixes #435

Review

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.69%. Comparing base (9ce312e) to head (ebc0446).
Report is 466 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #455      +/-   ##
===========================================
- Coverage    98.71%   98.69%   -0.02%     
===========================================
  Files           47       47              
  Lines         3025     2985      -40     
===========================================
- Hits          2986     2946      -40     
  Misses          39       39              

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[BradyPlanden]

Project coverage fails because this PR removes a large amount of code, but the number of missed line hits remains the same. All good for review.

[NicolaCourtier]

I'm going to remove the inputs argument from compute() to avoid the possibility of users passing parameters which do not match those used to make the prediction. Other than that, only a couple of minor comments and we should be good to merge.

[NicolaCourtier]

Thanks for these improvements!