Skip torch.compile tests on python 3.14

[Dan-Flores]

While preparing for the 0.9 release, the tests that utilize torch.compile failed on every python 3.14 build.
This PR adds a function get_python_version to get the current python version, and skip if at or above 3.14.

The main CI does not test on python 3.14 currently, so it has no effect currently.
I tested on a system using Python 3.14, and all the tests were skipped as expected:

test/test_decoders.py::TestVideoDecoder::test_compile[cpu] SKIPPED (torch.compile is not supported on Python 3.14+)
test/test_decoders.py::TestVideoDecoder::test_compile[cuda] SKIPPED (torch.compile is not supported on Python 3.14+)
test/test_decoders.py::TestVideoDecoder::test_compile[cuda:beta] SKIPPED (torch.compile is not supported on Python 3.14+)
test/test_ops.py::TestVideoDecoderOps::test_compile_seek_and_next[cpu] SKIPPED (torch.compile is not supported on Python 3.14+)
test/test_ops.py::TestVideoDecoderOps::test_compile_seek_and_next[cuda] SKIPPED (torch.compile is not supported on Python 3.14+)
test/test_ops.py::TestVideoDecoderOps::test_compile_seek_and_next[cuda:beta] SKIPPED (torch.compile is not supported on Python 3.14+)