Add NVIDIA provider models with standardized IDs

[d-oit]

This PR adds NVIDIA provider models with standardized IDs and organizes them into subfolders for better structure. Changes include:

• Reorganized NVIDIA models into subfolders based on provider (e.g., nvidia/, openai/, google/)
• Added standardized id fields to all models for consistency
• Updated README.md with optional instructions for model organization
• Removed outdated model configurations
• Added new model configurations with proper IDs

These changes ensure proper model identification, better organization, and integration with the models.dev platform.