New API: add_modeling_region()

[ansnfernand]

Checklist:

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

[codecov]

Codecov Report

Attention: Patch coverage is 41.12150% with 63 lines in your changes missing coverage. Please review.

Project coverage is 57.21%. Comparing base (8127837) to head (a73b72c).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/ansys/sherlock/core/layer.py	36.73%	62 Missing ⚠️
src/ansys/sherlock/core/errors.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #349      +/-   ##
==========================================
- Coverage   57.61%   57.21%   -0.40%     
==========================================
  Files          21       21              
  Lines        4327     4434     +107     
==========================================
+ Hits         2493     2537      +44     
- Misses       1834     1897      +63     

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