[BUG] Unreliable stdout capture on Windows causes sporadic test failures

Bug Description

CI test runs on multi-GPU and Debug setups for Windows sporadically produce errors like:

Number of potential bsr_mm blocks (4) exceeded max_nnz (2)

This error message is expected by test_bsr_mm_max_new_nnz, but instead gets detected by other tests as unexpected output.

It's a known issue that on Windows the StdOutCapture does not work reliably. This is currently worked around by not asserting when the output is empty, but that doesn't prevent the above issue.

We should instead skip all tests that expect to write to stdout, on Windows.

System Information

No response