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

---------

Co-authored-by: Arthur Zucker <arthur.zucker@gmail.com>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

setup.py

@@ -148,6 +148,7 @@ _deps = [
     "pyyaml>=5.1",
     "pydantic",
     "pytest>=7.2.0,<8.0.0",
+    "pytest-asyncio",
     "pytest-timeout",
     "pytest-xdist",
     "python>=3.9.0",
@@ -319,6 +320,7 @@ extras["tiktoken"] = deps_list("tiktoken", "blobfile")
 extras["testing"] = (
     deps_list(
         "pytest",
+        "pytest-asyncio",
         "pytest-rich",
         "pytest-xdist",
         "timeout-decorator",