chore(telemetry): code cleanup (#3897)

# What does this PR do?
Clean up telemetry code since the telemetry API has been remove.
- moved telemetry files out of providers to core
- removed from Api

## Test Plan

❯ OTEL_SERVICE_NAME=llama_stack
OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318 uv run llama stack run
starter
❯ curl http://localhost:8321/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-4o-mini",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }'

-> verify traces in Grafana

CI

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

@@ -8,8 +8,8 @@ import asyncio
 
 from llama_stack.apis.inference import Message
 from llama_stack.apis.safety import Safety, SafetyViolation, ViolationLevel
+from llama_stack.core.telemetry import tracing
 from llama_stack.log import get_logger
-from llama_stack.providers.utils.telemetry import tracing
 
 log = get_logger(name=__name__, category="agents::meta_reference")