New API: add_modeling_region()

[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
• [] 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 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 :warning:
src/ansys/sherlock/core/errors.py	88.88%	1 Missing :warning:

Additional details and impacted files

```diff @@ 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 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.