[PY] fix: StreamingResponse attributes shared between different Strea…

…mingResponse instances (#2321)

[PY] fix: StreamingResponse attributes shared between different
StreamingResponse instances

## Linked issues

closes: #2320 

## Details

Initializes `StreamingResponse` attributes for instance instead of
class. Each `StreamingResponse` will handle its own attributes, hence,
sequence number, queue and stream id.

#### Change details

**code snippets**:
```python
    def __init__(self, context: TurnContext) -> None:
        """
        Initializes a new instance of the `StreamingResponse` class.
        :param context: The turn context.
        """
        self._context = context
        self._next_sequence = 1
        self._stream_id = ""
        self._message = ""
        self._attachments = []
        self._ended = False
        self._citations = []
        self._sensitivity_label = None
        self._enable_feedback_loop = False
        self._feedback_loop_type = None
        self._enable_generated_by_ai_label = False
        self._queue = []
        self._queue_sync = None
        self._chunk_queued = False
```

## Attestation Checklist

- [X] My code follows the style guidelines of this project

- I have checked for/fixed spelling, linting, and other errors
- I have commented my code for clarity
- I have made corresponding changes to the documentation (updating the
doc strings in the code is sufficient)
- My changes generate no new warnings
- I have added tests that validates my changes, and provides sufficient
test coverage. I have tested with:
  - Local testing
  - E2E testing in Teams
- New and existing unit tests pass locally with my changes

### Additional information

> Feel free to add other relevant information below

python/packages/ai/teams/streaming/streaming_response.py

@@ -33,28 +33,41 @@ class StreamingResponse:
     """
 
     _context: TurnContext
-    _next_sequence: int = 1
-    _stream_id: str = ""
-    _message: str = ""
-    _attachments: List[Attachment] = []
-    _ended: bool = False
-
-    _citations: Optional[List[ClientCitation]] = []
-    _sensitivity_label: Optional[SensitivityUsageInfo] = None
-    _enable_feedback_loop: Optional[bool] = False
-    _feedback_loop_type: Optional[Literal["default", "custom"]] = None
-    _enable_generated_by_ai_label: Optional[bool] = False
-
-    _queue: List[Callable[[], Activity]] = []
-    _queue_sync: Optional[asyncio.Task] = None
-    _chunk_queued: bool = False
+    _next_sequence: int
+    _stream_id: str
+    _message: str
+    _attachments: List[Attachment]
+    _ended: bool
+
+    _citations: Optional[List[ClientCitation]]
+    _sensitivity_label: Optional[SensitivityUsageInfo]
+    _enable_feedback_loop: Optional[bool]
+    _feedback_loop_type: Optional[Literal["default", "custom"]]
+    _enable_generated_by_ai_label: Optional[bool]
+
+    _queue: List[Callable[[], Activity]]
+    _queue_sync: Optional[asyncio.Task]
+    _chunk_queued: bool
 
     def __init__(self, context: TurnContext) -> None:
         """
         Initializes a new instance of the `StreamingResponse` class.
         :param context: The turn context.
         """
         self._context = context
+        self._next_sequence = 1
+        self._stream_id = ""
+        self._message = ""
+        self._attachments = []
+        self._ended = False
+        self._citations = []
+        self._sensitivity_label = None
+        self._enable_feedback_loop = False
+        self._feedback_loop_type = None
+        self._enable_generated_by_ai_label = False
+        self._queue = []
+        self._queue_sync = None
+        self._chunk_queued = False
 
     @property
     def stream_id(self) -> str: