tests(cross-runtime-serde): hide torch-trt DLLs on Windows too

[tp5uiuc]

Description

tests/py/dynamo/models/_cross_runtime_load_helper.py:_hide_so_files() only globbed the
Linux/macOS-style libtorchtrt* pattern. On Windows the Torch-TensorRT runtime libraries
are named torchtrt.dll / torchtrt_runtime.dll (no lib prefix; see
py/torch_tensorrt/_features.py), so the glob returned an empty list and the spawned
Python-only subprocess kept torch_tensorrt_runtime == True, tripping the
C++ runtime should be disabled assertion.

Make the glob platform-aware:

• Windows: torchtrt*.dll, torchtrt*.lib
• Linux/macOS: libtorchtrt* (unchanged)

Fixes the three test_cross_runtime_serde.py failures on the Windows L2 dynamo compile
runners surfaced in #4330:

• test_save_cpp_load_python
• test_save_python_load_python
• test_save_python_load_cpp

Type of change

• Bug fix (test-only; no runtime API change)

Checklist:

• My code follows the style guidelines of this project (You can use the linters)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas and hacks
• I have made corresponding changes to the documentation
• I have added tests to verify my fix or my feature
• New and existing unit tests pass locally with my changes
• I have added the relevant labels to my PR in so that relevant reviewers are notified

[cehongwang]

LGTM