New API: export_FEA_model()

[ansnfernand]

Checklist:

• [x] Run unit tests and make sure they all pass
• [x] Check and fix style errors
  • pre-commit command line check
  • Problems tab in PyCharm
• [x] Bench test new/modified APIs by using and modifying the code in the example for the API method
• [x] Add new classes to rst files, located at: \doc\source\api
• [x] Generate documentation
• [x] Verify the HTML. It gets generated at: \doc\build\html.
  • Open index.html
  • Click on "API Reference" at the top.
  • Verify HTML for API changes.
• [x] Check that test code coverage is at least 80% when Sherlock is running and can be connected to using gRPC

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 51.89873% with 38 lines in your changes missing coverage. Please review.

Project coverage is 57.63%. Comparing base (1ca31ac) to head (510587f).

Files	Patch %	Lines
src/ansys/sherlock/core/model.py	44.11%	38 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #334 +/- ## ========================================== - Coverage 57.75% 57.63% -0.12% ========================================== Files 21 21 Lines 4244 4322 +78 ========================================== + Hits 2451 2491 +40 - Misses 1793 1831 +38 ```

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