--Enable override of default Attributes Registration checks

[jturner65]

Motivation and Context

Currently to register an object or stage attributes the specified render asset handle must exist, either as a valid object on disk, a valid existing primitive, or (in the case of a stage) be "none". If none of these conditions are true, the registration will fail and the attributes will not be added to the attributesManager library. This is useful in case errors exist in the attributes, so that object creation does not fail due to misnamed target assets.

The ability to override registration checks for object and stage attributes checks is useful for when render assets are computationally/"hand" crafted meshes. This PR adds a boolean argument to the registration process that allows for overriding the non-existing asset failure with a warning.

The default behavior will be to fail if specified render handle does not correspond to a known/knowable asset.

How Has This Been Tested

C++ and python tests pass

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.