Summary: MLflow 3 announced

Why It Matters: This shows a new main version of MLflow.

What Changed:

• Removed old release notes
• Removed old blog posts
• Removed survey link
• Added "MLflow 3" announcement
• Added new sections for "GenAI Apps & Agents" and "Model Training"
• Added "Self-hosted Open Source" and "Managed hosting ON" options
• Changed the main menu items
• Updated the "Trusted by" section