selftests: drv-net: test dumping qstats per device

Add a test for dumping qstats device by device.

ksft framework grows a ksft_raises() helper, to be used
under with, which should be familiar to unittest users.

Link: https://lore.kernel.org/r/20240420023543.3300306-5-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>