Closes#6137
- Add 'lmstudio' to the PROVIDERS list in CLI constants
- Add ENV_VARS configuration for LMStudio (model name, API base URL, API key)
- Support default_value in env var prompts for pre-filled defaults
- Default API base URL is http://localhost:1234/v1
- Add comprehensive tests for the LMStudio provider integration
Co-Authored-By: João <joao@crewai.com>