tests: skip TestPythonRuntimeAliasedIO on TensorRT-RTX with the C++ runtime

[tp5uiuc]

Description

What

Skip TestPythonRuntimeAliasedIO on TensorRT-RTX builds that also ship the C++
runtime, where it currently fails.

Why

The runtimes are expected to be either/or: the flavor is picked from whether
libtorchtrt.so is loaded, and every in-library TRTEngine construction site is
gated on that same flag. This class hand-builds a Python TRTEngine from packed
engine info regardless, producing a combination the library never does — a
torchbind-backed RuntimeCache asked to serve a Python engine. ensure_cache()
returns None there and set_runtime_cache rejects an explicitly-passed None,
so both tests in the class fail.

How

• test_aliased_io.py: skipIf(torch_tensorrt_runtime and tensorrt_rtx).
  Deliberately narrow — on standard TensorRT the runtime-config path is
  short-circuited in ensure_initialized, so a hand-built engine is harmless and
  the class stays live; it also stays live on python-only builds, where the
  Python TRTEngine is the real runtime and the test is the point.

Testing

Build	Result
C++ runtime, tests/py/dynamo/runtime/	170 passed, 46 skipped

The same suite on main reports 2 failed.

Type of change

• Bug fix (non-breaking change which fixes an issue)

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

[tp5uiuc]

[by Claude Code] Closing in favour of #4482, which fixes these tests rather than skipping them.

TestPythonRuntimeAliasedIO hand-builds a Python TRTEngine. That engine came
up with the default RuntimeSettings, whose runtime_cache is a path string;
RuntimeCache then picked its backing handle from whether the C++ runtime was
loaded, and on a C++ build ensure_cache() returned None, so
set_runtime_cache(None) raised. #4482 defaults engines to runtime_cache=None
— the module owns the implicit cache — so no attach happens and the failure goes
away at the source.

Verified on TensorRT-RTX/A100, runtime/test_aliased_io.py: 2 failed → 10
passed, on both the Python and C++ runtimes.