--Remove SUNCG dataset support/references

[jturner65]

Motivation and Context

This PR removes all support and references to SunCG dataset, to minimize clutter and potential for future support issues as we refactor and update mesh loading pipeline and support for semantic assets, dataset configs, etc.

How Has This Been Tested

locally c++ and python. Suncg test was removed.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.