feat(agents): add agent naming functionality (#1922)

# What does this PR do?
Allow users to name an agent and use the name in telemetry instead of
relying on randomly generated agent_ids. This improves the developer
experience by making it easier to find specific agents in telemetry
logs.

Closes #1832

## Test Plan

- Added tests to verify the agent name is properly stored and retrieved
- Ran `uv run -- pytest -v
tests/integration/telemetry/test_telemetry.py::test_agent_name_filtering`
from the root of the project and made sure the tests pass
- Ran `uv run -- pytest -v
tests/integration/telemetry/test_telemetry.py::test_agent_query_spans`
to verify existing code without agent names still works correctly

## Use Example
```
agent = Agent(
    llama_stack_client, 
    model=text_model_id, 
    name="CustomerSupportAgent",  # New parameter
    instructions="You are a helpful customer support assistant"
)
session_id = agent.create_session(f"test-session-{uuid4()}")
```

## Implementation Notes
- Agent names are optional string parameters with no additional
validation
- Names are not required to be unique - multiple agents can have the
same name
- The agent_id remains the unique identifier for an agent

---------

Co-authored-by: raghotham <raghotham@gmail.com>

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

@@ -178,6 +178,8 @@ class ChatAgent(ShieldRunnerMixin):
             span.set_attribute("request", request.model_dump_json())
             turn_id = str(uuid.uuid4())
             span.set_attribute("turn_id", turn_id)
+            if self.agent_config.name:
+                span.set_attribute("agent_name", self.agent_config.name)
 
         await self._initialize_tools(request.toolgroups)
         async for chunk in self._run_turn(request, turn_id):
@@ -190,6 +192,8 @@ class ChatAgent(ShieldRunnerMixin):
             span.set_attribute("session_id", request.session_id)
             span.set_attribute("request", request.model_dump_json())
             span.set_attribute("turn_id", request.turn_id)
+            if self.agent_config.name:
+                span.set_attribute("agent_name", self.agent_config.name)
 
         await self._initialize_tools()
         async for chunk in self._run_turn(request):
@@ -498,6 +502,8 @@ class ChatAgent(ShieldRunnerMixin):
             stop_reason = None
 
             async with tracing.span("inference") as span:
+                if self.agent_config.name:
+                    span.set_attribute("agent_name", self.agent_config.name)
                 async for chunk in await self.inference_api.chat_completion(
                     self.agent_config.model,
                     input_messages,