Automate HairStep Inference with Model Download, Setup, and Execution

[deepmancer]

This pull request simplifies the HairStep inference process by automating model downloads, module builds, and script execution. Configurations are more organized, and model and library handling is fully programmatic.

Key Updates:

• Modular Configs: Cleaner, structured configuration for easier management.
• Automated Model Download: Downloads SAM and OCC/ORIENT models if not already available (using curl and gdown).
• Module Build: Automatically builds the 3DDFA_V2 module.
• Script Execution: Runs all necessary inference scripts in order.