add init_pq option for PandaModels opf warm starts

[jerelang]

• PandaModels opf warm starts were only directly supported for voltage angle and magnitude, for active/reactive power warm starts creating the callback file was necessary
• adds optional init_pq parameter to the PandaModels opf runpm wrappers for active/reactive power starts
• when init_pq="results", adds pg_start and qg_start values to the PowerModels generator data from the net result tables
• also removes the unused init="flat" option from the PandaModels opf _add_opf_options calls

[codecov]

Codecov Report

❌ Patch coverage is 9.75610% with 37 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.29%. Comparing base (0c6a1f0) to head (c348b1a).

Files with missing lines	Patch %	Lines
pandapower/converter/pandamodels/to_pm.py	13.33%	26 Missing ⚠️
pandapower/runpm.py	0.00%	11 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2985      +/-   ##
===========================================
- Coverage    72.34%   72.29%   -0.05%     
===========================================
  Files          353      353              
  Lines        38828    38856      +28     
===========================================
+ Hits         28089    28091       +2     
- Misses       10739    10765      +26     

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[vogt31337]

@jerelang , thanks for the PR. Can you add a line to the changelog? And can you change the tests to use np.isclose for float comparison? Thanks!

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud