FEAT: Add method export_inception_voltage

[tizianrot]

Description

added method for Maxwell post- processing: export inception voltage evaluation results to file .

Issue linked

#6824

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate tests (unit, integration, system).
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved by the PR if any.
• I have agreed with the Contributor License Agreement (CLA).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.12%. Comparing base (dd059ff) to head (3653057).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6950      +/-   ##
==========================================
- Coverage   82.17%   81.12%   -1.06%     
==========================================
  Files         247      247              
  Lines       78563    78563              
==========================================
- Hits        64561    63734     -827     
- Misses      14002    14829     +827     

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[gmalinve]

LGTM