Add SciPyDifferentialEvolution optimiser

[BradyPlanden]

This PR adds:

• SciPyDifferentialEvolution optimiser
• Adds maxiter as argument to BaseOptimiser with functionality added to NLoptOptimize and SciPyMinimize
• Adds the required tests for coverage

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (f08d706) 92.59% compared to head (097bc51) 93.03%.
Report is 3 commits behind head on develop.

❗ Current head 097bc51 differs from pull request most recent head 707f16a. Consider uploading reports for the commit 707f16a to get more accurate results

Files	Patch %	Lines
pybop/optimisers/scipy_optimisers.py	96.15%	2 Missing ⚠️
pybop/_problem.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #132      +/-   ##
===========================================
+ Coverage    92.59%   93.03%   +0.44%     
===========================================
  Files           33       34       +1     
  Lines         1121     1178      +57     
===========================================
+ Hits          1038     1096      +58     
+ Misses          83       82       -1     

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[NicolaCourtier]

Hi @BradyPlanden, I added logging of the SciPy iterations to bring this branch up to speed with develop - this is the cause of the conflicts.

[NicolaCourtier]

Great work @BradyPlanden! Just one comment on the changelog and then all good to merge, thanks!