use logging instead of prints (#499)

# What does this PR do?

This PR moves all print statements to use logging. Things changed:
- Had to add `await start_trace("sse_generator")` to server.py to
actually get tracing working. else was not seeing any logs
- If no telemetry provider is provided in the run.yaml, we will write to
stdout
- by default, the logs are going to be in JSON, but we expose an option
to configure to output in a human readable way.

llama_stack/providers/remote/inference/ollama/ollama.py

@@ -4,6 +4,7 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import logging
 from typing import AsyncGenerator
 
 import httpx
@@ -39,6 +40,7 @@ from llama_stack.providers.utils.inference.prompt_adapter import (
     request_has_media,
 )
 
+log = logging.getLogger(__name__)
 
 model_aliases = [
     build_model_alias(
@@ -105,7 +107,7 @@ class OllamaInferenceAdapter(Inference, ModelsProtocolPrivate):
         return AsyncClient(host=self.url)
 
     async def initialize(self) -> None:
-        print(f"checking connectivity to Ollama at `{self.url}`...")
+        log.info(f"checking connectivity to Ollama at `{self.url}`...")
         try:
             await self.client.ps()
         except httpx.ConnectError as e: