selftests: ublk: add one stress test for covering IO vs. removing device

Add stress_test_01 for running IO vs. removing device for verifying that
ublk device removal can work as expected when heavy IO workloads are in
progress.

null, loop and loop/zc are covered in this tests.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250303124324.3563605-10-ming.lei@redhat.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>