Retain Python async run resources (#32041)
This pull request updates the ONNX Runtime Python bindings to improve
memory management and API flexibility for asynchronous inference
sessions. The main changes ensure that Python objects used as inputs to
`run_async` are properly referenced and not prematurely garbage
collected, and that the API is more Pythonic by accepting `py::object`
for session and run options. It also adds a test to verify that input
arrays are kept alive during asynchronous execution.
**Improvements to memory management and API flexibility:**
* The `AsyncResource` struct now stores references to Python feed
objects, the session, and run options to ensure they are kept alive for
the duration of async execution
(`onnxruntime/python/onnxruntime_pybind_state.cc`).
* The `run_async` binding now accepts `py::object` for the session and
run options, and internally casts them as needed. This makes the API
more Pythonic and flexible
(`onnxruntime/python/onnxruntime_pybind_state.cc`).
* When preparing feeds for `run_async`, the code now stores each input
object in `feed_objects` before creating the corresponding `OrtValue`,
ensuring the Python objects are not garbage collected too early
(`onnxruntime/python/onnxruntime_pybind_state.cc`).
**Testing and validation:**
* A test using `weakref` was added to verify that input arrays passed to
`run_async` remain alive until the callback is invoked, preventing
premature garbage collection
(`onnxruntime/test/python/onnxruntime_test_python.py`)
[[1]](diffhunk://#diff-bc2d3954a8ed883e3036dc7a675c7ba13b6299e1079728e7b6069cab1f49479cR690)
[[2]](diffhunk://#diff-bc2d3954a8ed883e3036dc7a675c7ba13b6299e1079728e7b6069cab1f49479cR702)
[[3]](diffhunk://#diff-bc2d3954a8ed883e3036dc7a675c7ba13b6299e1079728e7b6069cab1f49479cL712-R721).
* The test also exercises explicit deletion and garbage collection of
inputs, session, and run options to ensure robustness
(`onnxruntime/test/python/onnxruntime_test_python.py`).
