fix: support chat response data types enabling streaming of tool calls

[adubovik]

Resolves #31

Breaking changes

Dependencies

• bump lower bound on openai from 1.0.0 to 1.1.0, since 1.1.0 is the first version supporting tools.

Streaming chat completion response class

• changed the type of delta field in aidial_client.types.chat.response.ChoiceDelta datatype to accomodate streaming tool call chunks:

class ChoiceDelta(ExtraAllowModel):
    index: int
-    delta: Union[ChatCompletionMessage, ChunkEmptyDelta]
+    delta: ChatCompletionMessageDelta
    finish_reason: Optional[str] = None

• removed aidial_client.types.chat.response.ChunkEmptyDelta as redundant