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/utils/memory/vector_store.py

@@ -5,6 +5,7 @@
 # the root directory of this source tree.
 import base64
 import io
+import logging
 import re
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
@@ -16,13 +17,14 @@ import httpx
 import numpy as np
 from numpy.typing import NDArray
 from pypdf import PdfReader
-from termcolor import cprint
 
 from llama_models.llama3.api.datatypes import *  # noqa: F403
 from llama_models.llama3.api.tokenizer import Tokenizer
 
 from llama_stack.apis.memory import *  # noqa: F403
 
+log = logging.getLogger(__name__)
+
 ALL_MINILM_L6_V2_DIMENSION = 384
 
 EMBEDDING_MODELS = {}
@@ -35,7 +37,7 @@ def get_embedding_model(model: str) -> "SentenceTransformer":
     if loaded_model is not None:
         return loaded_model
 
-    print(f"Loading sentence transformer for {model}...")
+    log.info(f"Loading sentence transformer for {model}...")
     from sentence_transformers import SentenceTransformer
 
     loaded_model = SentenceTransformer(model)
@@ -92,7 +94,7 @@ def content_from_data(data_url: str) -> str:
         return "\n".join([page.extract_text() for page in pdf_reader.pages])
 
     else:
-        cprint("Could not extract content from data_url properly.", color="red")
+        log.error("Could not extract content from data_url properly.")
         return ""