Removed internal seed setting

[taraeicher]

Internally setting the seed leads to reproducible behavior but is a problem if the user wants to split the generation of null PANDA networks into chunks and then paste them (which can be more efficient). We therefore allow the user to set the seed as needed for their application.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.65%. Comparing base (ca4a54c) to head (fbf8567).
⚠️ Report is 2 commits behind head on devel.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #387      +/-   ##
==========================================
- Coverage   59.53%   57.65%   -1.89%     
==========================================
  Files          21       21              
  Lines        3517     3516       -1     
==========================================
- Hits         2094     2027      -67     
- Misses       1423     1489      +66     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.