Implement AsyncTextIteratorStreamer for asynchronous streaming (#34931)
* Add AsyncTextIteratorStreamer class
* export AsyncTextIteratorStreamer
* export AsyncTextIteratorStreamer
* improve docs
* missing import
* missing import
* doc example fix
* doc example output fix
* add pytest-asyncio
* first attempt at tests
* missing import
* add pytest-asyncio
* fallback to wait_for and raise TimeoutError on timeout
* check for TimeoutError
* autodoc
* reorder imports
* fix style
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Co-authored-by: Arthur Zucker <arthur.zucker@gmail.com>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>