MDEV-27900: aio handle partial reads/writes (uring)

MDEV-27900 continued for uring.

Also spell synchronously correctly in sql_parse.cc.

Reviewed by Wlad.

sql/sql_parse.cc

@@ -1190,7 +1190,7 @@ static enum enum_server_command fetch_command(THD *thd, char *packet)
     DISPATCH_COMMAND_CLOSE_CONNECTION  request of THD shutdown
           (s. dispatch_command() description)
   @retval
-    DISPATCH_COMMAND_WOULDBLOCK - need to wait for asyncronous operations
+    DISPATCH_COMMAND_WOULDBLOCK - need to wait for asynchronous operations
                                   to finish. Only returned if parameter
                                   'blocking' is false.
 */

tpool/aio_liburing.cc

@@ -161,6 +161,8 @@ class aio_uring final : public tpool::aio
       }
 
       io_uring_cqe_seen(&aio->uring_, cqe);
+      if (iocb->m_ret_len != iocb->m_len && !iocb->m_err)
+        finish_synchronous(iocb);
 
       // If we need to resubmit the IO operation, but the ring is full,
       // we will follow the same path as for any other error codes.