Refactor pipeline plot

[AurelienJaquier]

this has been tested with a luigi workflow and local access point

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 10.71429% with 25 lines in your changes missing coverage. Please review.

Project coverage is 52.43%. Comparing base (8d5b0ab) to head (ebcc9f7).
Report is 116 commits behind head on main.

Files with missing lines	Patch %	Lines
bluepyemodel/emodel_pipeline/plotting.py	8.33%	11 Missing ⚠️
bluepyemodel/tasks/emodel_creation/optimisation.py	0.00%	7 Missing ⚠️
bluepyemodel/tools/utils.py	22.22%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #175      +/-   ##
==========================================
- Coverage   60.07%   52.43%   -7.65%     
==========================================
  Files         109      124      +15     
  Lines        7838    10443    +2605     
==========================================
+ Hits         4709     5476     +767     
- Misses       3129     4967    +1838     

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