Python: [Bug]: OpenAI RAPI no longer requires the call id on a function call result

### Description

As described in the title: https://developers.openai.com/api/reference/resources/responses/methods/create#(resource)%20responses%20%3E%20(method)%20create%20%3E%20(params)%200.non_streaming%20%3E%20(param)%20input%20%3E%20(schema)%20%3E%20(variant)%201%20%3E%20(items)%20%3E%20(variant)%208%20%3E%20(property)%20call_id

Our OpenAI integration still requires a call_id on the function result content:
```
@classmethod
def from_function_result(
cls: type[ContentT],
call_id: str,
*,
result: Any = None,
exception: str | None = None,
annotations: Sequence[Annotation] | None = None,
additional_properties: MutableMapping[str, Any] | None = None,
raw_representation: Any = None,
) -> ContentT:
```

And our OpenAI integration drops function result contents that don't have a call id:
```
case "function_call":
if not content.call_id:
logger.warning(f"FunctionCallContent missing call_id for function '{content.name}'")
return {}
```

### Code Sample

This hasn't triggered any issue yeah but translating the function result contents between OpenAI spec compatible SDKs and MAF content type is awkward. The following code will raise a Pylance warning:

```
Content.from_function_result(item.get("call_id"), result=output)
"""
Argument of type "str | None" cannot be assigned to parameter "call_id" of type "str" in function "from_function_result"
Type "str | None" is not assignable to type "str"
"None" is not assignable to "str"
"""
```

### Package Versions

agent-framework-core, agent-framework-openai

### Additional Context

We need to check what the services actually expects.