Refactor update_capacity

[NicolaCourtier]

Description

Update the order in which the parameter_set is updated during design optimisation and move update_capacity to become an attribute of the problem.

Issue reference

Fixes #464

Review

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.04%. Comparing base (6b83edc) to head (121187c).
Report is 23 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #465      +/-   ##
===========================================
+ Coverage    99.01%   99.04%   +0.02%     
===========================================
  Files           52       52              
  Lines         3555     3545      -10     
===========================================
- Hits          3520     3511       -9     
+ Misses          35       34       -1     

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[BradyPlanden]

LGTM, thanks @NicolaCourtier. I'll merge once #484 lands.