[BE] - Error messages for physics specific API calls without implementation

[aclegg3]

Motivation and Context

Physics API calls made without Bullet installed or active return default values. This can cause confusion for users when the code runs, but returns unexpected values. For example, it should be clear that there are no ray cast hits because physics is not available rather than because the ray did not hit anything.

There could be an argument to make these warnings instead of errors. In either case, the code executes rather than crashing.

How Has This Been Tested

Locally in viewer application. CI test without physics active.

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.

[jturner65]

LGTM