t/jobs/t0035: add test for the file operations IO engine

t/jobs/t0035: add test for the file operations IO engine

The previous commit fixed the NULL pointer dereference which happened
when the write_lat_log option is specified for the file operations IO
engine. Add a new test case to confirm the fix. This test case also
covers the basic use cases of the file operations IO engine.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20240906023717.1464031-3-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>