Modifications to cartesian grid utilities

[anilyil]

Purpose

Few modifications to the cartesian background grid routines. We can specify if the outer BC of the cartesian extrusion is overset or farfield. We can also query grid objects for their bounding box and then explicitly provide bounding box coordinates for the cartesian grids.

Expected time until merged

1-2 weeks

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Checklist

• I have run flake8 and black to make sure the Python code adheres to PEP-8 and is consistently formatted
• I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation