chore: deprecate allow_turn_resume (#1377)

# What does this PR do?

- Deprecate allow_turn_resume flag as this is used for staying backward
compat.
- Closes https://github.com/meta-llama/llama-stack/issues/1363

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan
```
LLAMA_STACK_CONFIG=fireworks pytest -v tests/api/agents/test_agents.py --inference-model "meta-llama/Llama-3.3-70B-Instruct" --record-responses
```

<img width="1054" alt="image"
src="https://github.com/user-attachments/assets/d31de2d4-0953-41e1-a71a-7e1579fa351a"
/>


[//]: # (## Documentation)

llama_stack/providers/inline/agents/meta_reference/agent_instance.py

@@ -243,8 +243,7 @@ class ChatAgent(ShieldRunnerMixin):
                 steps=steps,
             )
             await self.storage.add_turn_to_session(request.session_id, turn)
-
-            if output_message.tool_calls and request.allow_turn_resume:
+            if output_message.tool_calls:
                 chunk = AgentTurnResponseStreamChunk(
                     event=AgentTurnResponseEvent(
                         payload=AgentTurnResponseTurnAwaitingInputPayload(
@@ -686,10 +685,16 @@ class ChatAgent(ShieldRunnerMixin):
                             message.content = [message.content] + output_attachments
                     yield message
                 else:
-                    logcat.debug("agents", f"completion message with EOM (iter: {n_iter}): {str(message)}")
+                    logcat.debug(
+                        "agents",
+                        f"completion message with EOM (iter: {n_iter}): {str(message)}",
+                    )
                     input_messages = input_messages + [message]
             else:
-                logcat.debug("agents", f"completion message (iter: {n_iter}) from the model: {str(message)}")
+                logcat.debug(
+                    "agents",
+                    f"completion message (iter: {n_iter}) from the model: {str(message)}",
+                )
                 # 1. Start the tool execution step and progress
                 step_id = str(uuid.uuid4())
                 yield AgentTurnResponseStreamChunk(

llama_stack/providers/inline/agents/meta_reference/agents.py

@@ -140,7 +140,6 @@ class MetaReferenceAgentsImpl(Agents):
         documents: Optional[List[Document]] = None,
         stream: Optional[bool] = False,
         tool_config: Optional[ToolConfig] = None,
-        allow_turn_resume: Optional[bool] = False,
     ) -> AsyncGenerator:
         request = AgentTurnCreateRequest(
             agent_id=agent_id,
@@ -150,7 +149,6 @@ class MetaReferenceAgentsImpl(Agents):
             toolgroups=toolgroups,
             documents=documents,
             tool_config=tool_config,
-            allow_turn_resume=allow_turn_resume,
         )
         if stream:
             return self._create_agent_turn_streaming(request)