Add import export formats

[ctreffs]

Description

• Adds Assimp namespace enum
• Adds import format checks and listings
• Adds export format listings
• AiFace cleanups

Checklist

• I've read the Contribution Guidelines
• I've followed the coding style of the rest of the project.
• I've added tests covering all new code paths my change adds to the project (to the extent possible).
• I've verified that my change does not break any existing tests or introduce unexpected benchmark regressions.
• I've updated the documentation (if appropriate).