[Data] Add -s flag to test_backpressure_e2e.py (ray-project#58977)

## Description

`test_backpressure_e2e` occasionally fails without any traceback or
warning message:
```
[2025-11-24T21:42:12Z] ==================== Test output for //python/ray/data:test_backpressure_e2e:
--
[2025-11-24T21:42:12Z] /opt/miniforge/lib/python3.12/site-packages/paramiko/pkey.py:82: CryptographyDeprecationWarning: TripleDES has been moved to cryptography.hazmat.decrepit.ciphers.algorithms.TripleDES and will be removed from cryptography.hazmat.primitives.ciphers.algorithms in 48.0.0.
[2025-11-24T21:42:12Z]   "cipher": algorithms.TripleDES,
[2025-11-24T21:42:12Z] /opt/miniforge/lib/python3.12/site-packages/paramiko/transport.py:253: CryptographyDeprecationWarning: TripleDES has been moved to cryptography.hazmat.decrepit.ciphers.algorithms.TripleDES and will be removed from cryptography.hazmat.primitives.ciphers.algorithms in 48.0.0.
[2025-11-24T21:42:12Z]   "class": algorithms.TripleDES,
[2025-11-24T21:42:12Z] ============================= test session starts ==============================
[2025-11-24T21:42:12Z] platform linux -- Python 3.12.9, pytest-7.4.4, pluggy-1.3.0 -- /opt/miniforge/bin/python3
[2025-11-24T21:42:12Z] cachedir: .pytest_cache
[2025-11-24T21:42:12Z] rootdir: /root/.cache/bazel/_bazel_root/1df605deb6d24fc8068f6e25793ec703/execroot/io_ray
[2025-11-24T21:42:12Z] configfile: pytest.ini
[2025-11-24T21:42:12Z] plugins: repeat-0.9.3, anyio-3.7.1, fugue-0.8.7, aiohttp-1.1.0, asyncio-0.17.2, docker-tools-3.1.3, forked-1.4.0, pytest_httpserver-1.1.3, lazy-fixtures-1.1.2, mock-3.14.0, remotedata-0.3.2, rerunfailures-11.1.2, sphinx-0.5.1.dev0, sugar-0.9.5, timeout-2.1.0, typeguard-2.13.3
[2025-11-24T21:42:12Z] asyncio: mode=Mode.AUTO
[2025-11-24T21:42:12Z] timeout: 180.0s
[2025-11-24T21:42:12Z] timeout method: signal
[2025-11-24T21:42:12Z] timeout func_only: False
[2025-11-24T21:42:12Z] collecting ... collected 12 items
[2025-11-24T21:42:12Z]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_large_e2e_backpressure_no_spilling PASSED [  8%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_small_cluster_resources[False-3-500] PASSED [ 16%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_small_cluster_resources[False-4-100] PASSED [ 25%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_small_cluster_resources[False-3-100] PASSED [ 33%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_small_cluster_resources[True-3-500] PASSED [ 41%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_small_cluster_resources[True-4-100] PASSED [ 50%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_small_cluster_resources[True-3-100] PASSED [ 58%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_resource_contention[False] PASSED [ 66%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_on_resource_contention[True] PASSED [ 75%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_no_deadlock_with_preserve_order PASSED [ 83%]
[2025-11-24T21:42:12Z] python/ray/data/tests/test_backpressure_e2e.py::test_input_backpressure_e2e PASSED [ 91%]================================================================================
```

To make this easier to debug, this PR enables the `-s` flag to log more
information.

Signed-off-by: Balaji Veeramani <bveeramani@berkeley.edu>

Author: bveeramani

python/ray/data/tests/test_backpressure_e2e.py

@@ -338,4 +338,4 @@ def __call__(self, df: np.ndarray):
 if __name__ == "__main__":
     import sys
 
-    sys.exit(pytest.main(["-v", __file__]))
+    sys.exit(pytest.main(["-sv", __file__]))