This pull request includes updates to the langtest package to improve model handling and dependency management. The most important changes include modifications to the load_model method to handle different model types and updates to the pyproject.toml file for dependency version upgrades and additions.

Improvements to model handling:

• langtest/modelhandler/llm_modelhandler.py: Modified the load_model method to include additional checks for chat_models attributes and raise a ValueError if the model is not found.

Dependency updates:

• pyproject.toml: Updated the mlflow dependency version from ^2.16.2 to ^2.18.0.
• pyproject.toml: Updated the pillow dependency version from 10.0.0 to ^11.0.0.
• pyproject.toml: Added langchain-community to the openai and databricks dependency groups.