Patch forward ref bug (#12508)

Currently this gives a bug:
```
from langchain.schema.runnable import RunnableLambda

bound = RunnableLambda(lambda x: x).with_config({"callbacks": []})

# ConfigError: field "callbacks" not yet prepared so type is still a ForwardRef, you might need to call RunnableConfig.update_forward_refs().
```

Rather than deal with cyclic imports and extra load time, etc., I think
it makes sense to just have a separate Callbacks definition here that is
a relaxed typehint.

libs/langchain/langchain/schema/runnable/config.py

@@ -32,6 +32,10 @@ if TYPE_CHECKING:
         CallbackManager,
         CallbackManagerForChainRun,
     )
+else:
+    # Pydantic validates through typed dicts, but
+    # the callbacks need forward refs updated
+    Callbacks = Optional[Union[List, Any]]
 
 
 class EmptyDict(TypedDict, total=False):

libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py

@@ -60,7 +60,11 @@ from langchain.schema.runnable import (
     RunnableSequence,
     RunnableWithFallbacks,
 )
-from langchain.schema.runnable.base import ConfigurableField, RunnableGenerator
+from langchain.schema.runnable.base import (
+    ConfigurableField,
+    RunnableBinding,
+    RunnableGenerator,
+)
 from langchain.schema.runnable.utils import (
     ConfigurableFieldMultiOption,
     ConfigurableFieldSingleOption,
@@ -3999,3 +4003,11 @@ async def test_runnable_gen_transform() -> None:
 
     assert list(chain.stream(3)) == [1, 2, 3]
     assert [p async for p in achain.astream(4)] == [1, 2, 3, 4]
+
+
+def test_with_config_callbacks() -> None:
+    result = RunnableLambda(lambda x: x).with_config({"callbacks": []})
+    # Bugfix from version 0.0.325
+    # ConfigError: field "callbacks" not yet prepared so type is still a ForwardRef,
+    # you might need to call RunnableConfig.update_forward_refs().
+    assert isinstance(result, RunnableBinding)