Unify client SDK loggers

[ashwinb]

Having two loggers is confusing. Let's have one.

This change is backward compatible. Older code will continue to work.

API is

for event in EventStreamPrinter.gen(inference.chat_completion(...):
   event.print()

Test Plan

$ llama-stack-client inference chat-completion --message "Hi how are you" --stream
Assistant> I'm just a language model, I don't have emotions or feelings like humans do, but I'm functioning properly and ready to help with any questions or tasks you may have! How about you? How's your day going so far?
$

cd llama-stack/tests/client-sdk
LLAMA_STACK_BASE_URL=http://localhost:8321 pytest -s -v agents/test_agents.py -k agent_simple