feat(chat): add tool calls, response format and system fingerprint

[aallam]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Related Issue	#252, Fix #254

Describe your change

Add new chat completions features and fields:

• Tool Calls
• Response format
• System fingerprint

[pwerry]

Thanks for this @aallam ! Do you plan to cut a release today?

[aallam]

@pwerry I'm hoping to add the other new beta features from OpenAI, such as assistants, threads, messages, and runs, before the release. However, if you want to start testing things out, you can use the snapshot release and share your feedback if anything is wrong or missing

[st4ycool]

Assistant API is added, but there is no way to create a thread yet, right?

[aallam]

@st4ycool not yet, working on adding it asap :)