[FEA]: Turn pytest warnings into errors

[rwgk]

As suggested by @shwina here:

• cuda.parallel: Forbid non-contiguous arrays as inputs (or outputs) #3233 (comment)

For easy future reference, this is the suggested pyproject.toml change:

• https://github.com/rapidsai/cudf/blob/955b1f4566abccf920a022dc78a1e654acf0de16/python/cudf/pyproject.toml#L97-L100

[tool.pytest.ini_options]
filterwarnings = [
    "error",
    "ignore:::.*xdist.*",
    "ignore:::.*pytest.*",
]