Python: Use openai assistant methods not azure ai (microsoft#10947)

### Motivation and Context

The OpenAI assistant code is using an import from the AzureAIAgent
related code, and when not installing the `azure` extras, this causes an
import error.

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### Description

Use OpenAI assistant specific thread action code.
- Closes microsoft#10942

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### Contribution Checklist

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- [X] The code builds clean without any errors or warnings
- [X] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [X] All unit tests pass, and I have added new tests where possible
- [X] I didn't break anyone 😄

Author: moonbox3

python/semantic_kernel/agents/open_ai/assistant_content_generation.py

@@ -476,3 +476,20 @@ def generate_streaming_annotation_content(
         start_index=annotation.start_index,
         end_index=annotation.end_index,
     )
+
+
+@experimental
+def generate_function_call_streaming_content(
+    agent_name: str,
+    fccs: list[FunctionCallContent],
+) -> StreamingChatMessageContent:
+    """Generate function call content.
+
+    Args:
+        agent_name: The agent name.
+        fccs: The function call contents.
+
+    Returns:
+        StreamingChatMessageContent: The chat message content containing the function call content as the items.
+    """
+    return StreamingChatMessageContent(role=AuthorRole.ASSISTANT, choice_index=0, name=agent_name, items=fccs)  # type: ignore

python/semantic_kernel/agents/open_ai/assistant_thread_actions.py

@@ -17,11 +17,11 @@
     ToolCallsStepDetails,
 )
 
-from semantic_kernel.agents.azure_ai.agent_content_generation import generate_function_call_streaming_content
 from semantic_kernel.agents.open_ai.assistant_content_generation import (
     generate_code_interpreter_content,
     generate_final_streaming_message_content,
     generate_function_call_content,
+    generate_function_call_streaming_content,
     generate_function_result_content,
     generate_message_content,
     generate_streaming_code_interpreter_content,