io_uring: add trace event for running task work

This is useful for investigating if task_work is batching

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220622134028.2013417-8-dylany@fb.com


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