ESSOptimizer: allow passing an optimizer factory

[dweindl]

Allow passing a optimizer factory to ESSOptimizer so that overall ESS walltime and function evaluation limits can be respected by the local optimizer.

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (4507747) 81.60% compared to head (6ce511c) 81.59%.

Files	Patch %	Lines
pypesto/optimize/ess/ess.py	84.61%	2 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1181      +/-   ##
===========================================
- Coverage    81.60%   81.59%   -0.02%     
===========================================
  Files          148      148              
  Lines        11704    11713       +9     
===========================================
+ Hits          9551     9557       +6     
- Misses        2153     2156       +3     

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[PaulJonasJost]

Looks good to me. Should we add checks for the optimisers, whether they support wall time?

[dweindl]

Looks good to me. Should we add checks for the optimisers, whether they support wall time?

I had similar thoughts. For this application I went for passing a callable where the user needs to see whether/how a given optimizer can handle those constraints. That works. If there are more use cases, one could think about adding Optimizer.set_maxtime, Optimizer.set_maxiter, .... to have a common interface for common options. Not sure, though, how much that would be used.