Update Foundry Toolkit model documentation

[Bob Tabor (bobtabor-msft)]

Summary

This PR updates the Foundry Toolkit model documentation for VS Code.

Changes include:

• Clarifying supported model sources, including Microsoft Foundry, Microsoft Foundry on Windows, Foundry Local, ONNX, Ollama, publisher-hosted models, and custom BYOM endpoints
• Adding a supported model sources table
• Updating model catalog filtering and category descriptions
• Revising add-model, deployment, Ollama, and model management guidance
• Removing outdated GitHub Models-specific guidance
• Updating model catalog screenshots

[Nick Trogh (ntrogh)]

Bob Tabor (@bobtabor-msft) Same as the other PR, updating images in-place will give users the old, cached version for a while.