PR #10433: Fixes type annotation overload of dlpack_managed_tensor_to_buffer in python/xla_extension

Imported from GitHub PR #10433

Encountered bug in jax-ml/jax#20175 (see this [comment](jax-ml/jax#20175 (comment))).

This adjusts the stub file to properly overload `dlpack_managed_tensor_to_buffer` so that both signatures can be checked against.
Copybara import of the project:

--
75cabb5 by Meekail Zain <zainmeekail@gmail.com>:

Update

Merging this change closes #10433

COPYBARA_INTEGRATE_REVIEW=#10433 from Micky774:type_update 75cabb5
PiperOrigin-RevId: 615973838

Author: Micky774

xla/python/xla_extension/__init__.pyi

@@ -700,9 +700,16 @@ class DeviceTopology:
 def buffer_to_dlpack_managed_tensor(
     buffer: ArrayImpl, stream: int | None = None
 ) -> Any: ...
+@overload
 def dlpack_managed_tensor_to_buffer(
     tensor: Any, device: Device, stream: int | None
 ) -> ArrayImpl: ...
+@overload
+def dlpack_managed_tensor_to_buffer( # Legacy overload
+    tensor: Any,
+    cpu_backend: Optional[Client] = ...,
+    gpu_backend: Optional[Client] = ...,
+) -> ArrayImpl: ...
 
 def cuda_array_interface_to_buffer(
     cai: Dict[str, Union[
@@ -714,12 +721,6 @@ def cuda_array_interface_to_buffer(
     gpu_backend: Optional[Client] = ...,
 ) -> ArrayImpl: ...
 
-# Legacy overload
-def dlpack_managed_tensor_to_buffer(
-    tensor: Any,
-    cpu_backend: Optional[Client] = ...,
-    gpu_backend: Optional[Client] = ...,
-) -> ArrayImpl: ...
 
 # === BEGIN py_traceback.cc