cad/openvsp: update to 3.31.0

Features:

• Trick or treat? Halloween mystery feature...
• Add structural assemblies made from multiple structures.
• Add rigid connections between structures in assembly.
• Add boundary condition specification to structures.
• Add aero-structure coupled problem GUI using CalculiX and VSPAERO.
• Split FEA Mesh generation from writing to file.
• Also split FEA CAD file generation and export from Meshing.
• Keep FEA Mesh in-memory, allowing more flexible workflow.
• Re-arranged menus to group structures and aero analyses.
• Build RPM packages for RedHat-based distributions.
• Add aerodynamic center stability mode to GUI.
• Force NACA 6A series to use a=0.8 camber line.
• Remove VSPAERO single analysis from API - reduce code duplication.

Bug Fixes:

• Allow non-unique names in pull-down menus.
• Make environment.yml match Python version.
• Fix component IDs passed to *.vspgeom. Fixes propellers.
• Write NORMAL at all B32 nodes, not just the first.
• Fix exporting symmetrical propeller at origin to STL.
• Insert FixPoins before InitMesh -- guarantee Fix Points
• Lots of VSPAERO fixes
• Lots of structures fixes