[Concurrency] Prefer swift_auth_code_function over swift_auth_code

This allows us to use constants, and not hardcoded numbers

Author: ktoso

stdlib/public/Concurrency/Task.cpp

@@ -1763,7 +1763,8 @@ swift_task_addCancellationHandlerImpl(
     void *context) {
   void *allocation =
       swift_task_alloc(sizeof(CancellationNotificationStatusRecord));
-  auto unsigned_handler = swift_auth_code(handler, 3848);
+  auto unsigned_handler = swift_auth_code_function(handler,
+      SpecialPointerAuthDiscriminators::CancellationNotificationFunction);
   auto *record = ::new (allocation)
       CancellationNotificationStatusRecord(unsigned_handler, context);
 
@@ -1816,7 +1817,8 @@ swift_task_addPriorityEscalationHandlerImpl(
     void *context) {
   void *allocation =
       swift_task_alloc(sizeof(EscalationNotificationStatusRecord));
-  auto unsigned_handler = swift_auth_code(handler, 30817);
+  auto unsigned_handler = swift_auth_code_function(handler,
+      SpecialPointerAuthDiscriminators::EscalationNotificationFunction);
   auto *record = ::new (allocation)
       EscalationNotificationStatusRecord(unsigned_handler, context);