AP_Scheduler: add field "name" to task structure for logging purposes

That field will be useful for logging as it is easier to know what task a log
is related to by using the task's name rather than using the number.

libraries/AP_Scheduler/AP_Scheduler.h

@@ -45,6 +45,7 @@ public:
 
     struct Task {
         task_fn_t function;
+        const char *name;
         uint16_t interval_ticks;
         uint16_t max_time_micros;
     };