Fix up safety client for versioned API

[stevegrubb]

When running:
python -m llama_stack.apis.safety.client localhost 5000

The API server was logging:
INFO: ::1:57176 - "POST /safety/run_shield HTTP/1.1" 404 Not Found

This patch uses the versioned API, uses the updated safety endpoint, and updates the model name to what's being served. The above python command now demonstrates a passing and failing example.

[ashwinb]

@stevegrubb We will be deleting these client.py files which served two purposes initially -- they were used as REST clients but also had some easy-to-use testing functionality which developers used when working with the stack server. Now, the client functionality has moved to https://github.com/meta-llama/llama-stack/blob/main/llama_stack/distribution/client.py. Tests have moved to either pytest or examples in llama-stack-apps.