Add a simplification step to cpp region parsing.

[GuySten]

Description

This PR adds a simplification step to region parsing.
This is done to fix parsing of complicated region definitions that are written outside the python API.

Fixes #3685.

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 15) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[GuySten]

Closing in favor of #3730.