core: Improve Runnable __or__ method typing annotations (#31273)

* It is possible to chain a `Runnable` with an `AsyncIterator` as seen
in `test_runnable.py`.
* Iterator and AsyncIterator Input/Output of Callables must be put
before `Callable[[Other], Any]` otherwise the pattern matching picks the
latter.

libs/core/langchain_core/prompts/structured.py

@@ -1,6 +1,6 @@
 """Structured prompt template for a language model."""
 
-from collections.abc import Iterator, Mapping, Sequence
+from collections.abc import AsyncIterator, Iterator, Mapping, Sequence
 from typing import (
     Any,
     Callable,
@@ -123,8 +123,9 @@ class StructuredPrompt(ChatPromptTemplate):
         self,
         other: Union[
             Runnable[Any, Other],
-            Callable[[Any], Other],
             Callable[[Iterator[Any]], Iterator[Other]],
+            Callable[[AsyncIterator[Any]], AsyncIterator[Other]],
+            Callable[[Any], Other],
             Mapping[str, Union[Runnable[Any, Other], Callable[[Any], Other], Any]],
         ],
     ) -> RunnableSerializable[dict, Other]:
@@ -134,8 +135,9 @@ class StructuredPrompt(ChatPromptTemplate):
         self,
         *others: Union[
             Runnable[Any, Other],
-            Callable[[Any], Other],
             Callable[[Iterator[Any]], Iterator[Other]],
+            Callable[[AsyncIterator[Any]], AsyncIterator[Other]],
+            Callable[[Any], Other],
             Mapping[str, Union[Runnable[Any, Other], Callable[[Any], Other], Any]],
         ],
         name: Optional[str] = None,