fix: normalize LLM parameter case and improve type handling

[devin-ai-integration[bot]]

Fix LLM Parameter Case Normalization and Type Handling

Description

This PR addresses issue #1817 by implementing proper case normalization for the LLM parameter and improving type handling for all LLM-related parameters.

Changes

• Add case normalization for 'LLM' parameter with deprecation warning
• Add comprehensive type conversion for LLM parameters (int, float, bool, dict, list)
• Add proper error handling for parameter conversion
• Add tests to verify parameter handling

Testing

• Added unit tests to verify:
  • Case-insensitive LLM parameter handling
  • Proper type conversion for different parameter types
  • Deprecation warning for uppercase 'LLM' usage
  • Environment variable handling

Implementation Details

• Implemented in post_init_setup method of Agent class
• Added type conversion for:
  • Integer parameters (timeout, max_tokens, etc.)
  • Float parameters (temperature, top_p, etc.)
  • Boolean parameters (logprobs)
  • Dictionary parameters (logit_bias)
  • List parameters (callbacks)
• Added comprehensive error handling for each type conversion

Link to Devin run: https://app.devin.ai/sessions/ac96d6577a1c435c9d0e48744b2bb04f

Fixes #1817