t/zbd: add the test cases to confirm continue_on_error option

t/zbd: add the test cases to confirm continue_on_error option

When the continue_on_error option is specified, it is expected that
write workloads do not stop even when bad blocks cause IO errors and
leave partially written data. Add a test cases to confirm it with
zonemode=zbd and the new option recover_zbd_write_error.

To create the IO errors as expected, use null_blk and scsi_debug.
Especially, use null_blk and its parameters badblocks and
badblocks_once, which can control the block to cause the IO error.
Introduce helper functions which confirms the parameters for bad blocks
are available, and sets up the bad blocks.

Using the helper functions, add four new test cases. The first two cases
confirm that the fio recovers after the IO error with partial write.
One test case covers psync IO engine. The other test case covers async
IO with libaio engine with high queue depth and multiple jobs. The last
two test cases confirm the case that another IO error happen again
during the recovery process from the IO error.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20250425052148.126788-8-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>