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/inline/safety/prompt_guard/prompt_guard.py

@@ -4,10 +4,10 @@
 # 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 Any, Dict, List
 
 import torch
-from termcolor import cprint
 
 from transformers import AutoModelForSequenceClassification, AutoTokenizer
 
@@ -20,6 +20,7 @@ from llama_stack.providers.datatypes import ShieldsProtocolPrivate
 
 from .config import PromptGuardConfig, PromptGuardType
 
+log = logging.getLogger(__name__)
 
 PROMPT_GUARD_MODEL = "Prompt-Guard-86M"
 
@@ -93,9 +94,8 @@ class PromptGuardShield:
         probabilities = torch.softmax(logits / self.temperature, dim=-1)
         score_embedded = probabilities[0, 1].item()
         score_malicious = probabilities[0, 2].item()
-        cprint(
+        log.info(
             f"Ran PromptGuardShield and got Scores: Embedded: {score_embedded}, Malicious: {score_malicious}",
-            color="magenta",
         )
 
         violation = None