text: Title: [Feature]: Add Warning for Chat Template Mismatches similar to SGLang
  Body: I'm requesting a feature to add warnings when users supply a chat template that differs from the official template for a particular model. Currently, vLLM simply acknowledges the supplied template without alerting users to potential performance issues.
  
  **Current Behavior:**
  When using a wrong chat template with vLLM, it only logs:
  ```
  Using supplied chat template:
  {% for message in messages %}{% if message.role == 'user' %}{{ message.content }}{% endif %}{% endfor %}
  ```
  
  **Requested Behavior:**
  While SGLang provides this helpful warning:
  ```
  Using a chat_template: 'None', which is different from official chat template: 'llama-3-instruct', This discrepancy may lead to performance degradation.
  ```
  
  I think that would improve the user experience by making potential issues more visible before they cause problems in production.
  
  ### Alternatives
  
  _No response_
  
  ### Additional context
  
  _No response_
  
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