kernel: work: check handler when submit to queue

Assert that the handler of a work is not NULL when submitting
it to the queue. This allows early detection of the
code that is submitting a non-NULL work with NULL handler to
the work queue (where it happens), rather than right before the
work item get executed in the queue (when it happens).

Signed-off-by: Yong Cong Sin <ycsin@meta.com>

kernel/work.c

@@ -370,6 +370,7 @@ int z_work_submit_to_queue(struct k_work_q *queue,
 		  struct k_work *work)
 {
 	__ASSERT_NO_MSG(work != NULL);
+	__ASSERT_NO_MSG(work->handler != NULL);
 
 	k_spinlock_key_t key = k_spin_lock(&lock);