Port stage_requires_lighting arg to python viewer

[aclegg3]

Motivation and Context

This argument allows terminal override of stage lighting defaults to enable synthetic lighting for scenes which require it but may not be configured to use it automatically.

How Has This Been Tested

Locally with stage assets which crash when rendered with flat shader.

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.