[Pytest][TensorRT] Mark the TensorRT tests with tvm.testing.requires_…

…cuda

Previously, the tests had an early bailout if tensorrt was disabled,
or if there was no cuda device present.  However, the tests were not
marked with `pytest.mark.gpu` and so they didn't run during
`task_python_integration_gpuonly.sh`.  This commit adds the
`requires_cuda` mark, and maintains the same behavior of testing the
tensorrt compilation steps if compilation is enabled, and running the
results if tensorrt is enabled.

In addition, some of the tests result in failures when run.  These
have been marked with `pytest.mark.xfail`, and are being tracked in
issue apache#8901.