chore: avoid some warnings when running cuda.core tests

[juenglin]

Fix pytest warnings in cuda_core test suite

Register the thread_unsafe and parallel_threads_limit custom marks in
pytest.ini to eliminate PytestUnknownMarkWarning noise across the suite.

Wrap itertools.combinations(...) arguments in list() in
test_object_protocols.py to fix PytestRemovedIn10Warning about passing
lazy iterators to @pytest.mark.parametrize (deprecated ahead of pytest 10).

Add @pytest.mark.filterwarnings("ignore::DeprecationWarning") to
test_temperature in test_system_device.py. The test exercises
get_threshold for all threshold types, including the four that
intentionally emit a DeprecationWarning on Ada+ hardware. The warning
behaviour itself is covered by the dedicated
test_temperature_threshold_unrecognized_device_arch test.

[github-actions]

Doc Preview CI
Preview removed because the pull request was closed or merged.