end2end CPU support

[yogeshchandrasekharuni]

Added CPU-only devices support

Description

• main_end2end now checks if "cuda" is not available, and if so, defaults to CPU.

Motivation and Context

• Now allows inferencing on devices with no cuda-enabled GPUs

How Has This Been Tested?

• Tested locally on custom animations

Types of changes

• 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:

• I have signed the Adobe Open Source CLA.
• 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 added tests to cover my changes.
• All new and existing tests passed.