Fix view_controller_chains

[christophfroehlich]

This reverts #812 and fixes #1095: python3-graphviz IS available as rosdep, and produces the desired output. I don't see the necessity to use pygraphviz, unless someone can fix the code for real.

Before (example_16)

After

I also added a --save option to save the output as PDF in the current directory instead of viewing it.

There is still something wrong in the representation, I'll keep it as draft.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.33%. Comparing base (3755e03) to head (b91b5ee).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2026      +/-   ##
==========================================
- Coverage   89.34%   89.33%   -0.01%     
==========================================
  Files         132      132              
  Lines       14688    14686       -2     
  Branches     1269     1269              
==========================================
- Hits        13123    13120       -3     
- Misses       1090     1092       +2     
+ Partials      475      474       -1     

Flag	Coverage Δ
unittests	89.33% <ø> (-0.01%)	⬇️

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see 5 files with indirect coverage changes

[Juliaj]

Thank you so much to fix this. The new graph generated makes way more sense than the previous one 😀 .