Fix azure openai coding error

[MonsterCoder]

Describe the changes you have made:

1. Fix merge_delta error while trying to concatenate None value to str.
2. Add an argument --no_llm_supports_function_calls. Some of Azure OpenAI models don't support functions calling. Current implementation logic to auto detect function-calling support is based on name matching. If a model is wrongly detected as supporting function_calls, it will throw error when it aptampts to execute code.

Reference any relevant issues (e.g. "Fixes #000"):

Fixes #919 #899

Pre-Submission Checklist (optional but appreciated):

• [ x] I have included relevant documentation updates (stored in /docs)
• [ x] I have read docs/CONTRIBUTING.md
• [ x] I have read docs/ROADMAP.md

OS Tests (optional but appreciated):

• [x ] Tested on Windows
• [ ] Tested on MacOS
• [ ] Tested on Linux