Cid/async tracing

[gustavocidornelas]

Summary

• The trace_async_openai wrapper was not working correctly when stream=True, raising the error:

TypeError: object async_generator can't be used in 'await' expression

• 35d0232 fixes this issue, by handling the AsyncIterator iterator correctly.
• 37f8ca0 exposes the trace_async_openai and trace_async methods at the top level of the lib, so that they can be conveniently imported as in:

from openlayer.lib import trace_async_openai, trace_async

• f63d990 fixes the issue where the Azure OpenAI chat completion steps were added alongside a redundant OpenAI chat completion step.