[RTR] refactor(maintaining plots)

[Ipuch]

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This change is 

[codecov]

Codecov Report

Attention: Patch coverage is 43.24324% with 42 lines in your changes are missing coverage. Please review.

Project coverage is 78.25%. Comparing base (7494252) to head (944c2fe).
Report is 48 commits behind head on master.

Files	Patch %	Lines
bioptim/gui/online_callback.py	33.33%	42 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #855   +/-   ##
=======================================
  Coverage   78.25%   78.25%           
=======================================
  Files         139      140    +1     
  Lines       16228    16230    +2     
=======================================
+ Hits        12699    12701    +2     
  Misses       3529     3529           

Flag	Coverage Δ
unittests	78.25% <43.24%> (+<0.01%)	⬆️

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[pariterre]

Reviewed 1 of 3 files at r1, 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Ipuch)