ai-plugin: Enhance LangChain manager with advanced tool processing

- Add comprehensive tool response processing and validation
- Implement intelligent message preparation for tool contexts
- Add specialized system prompts for tool response handling
- Improve tool call alignment validation and error handling
- Add content size management to prevent memory issues
- Enhance user context building with conversation history and tool results
- Support multiple provider compatibility (Azure, Anthropic, etc.)

Signed-off-by: ashu8912 <aghildiyal@microsoft.com>

Author: ashu8912