Expand return code values returned by TQM and strategies

This allows the PlaybookExecutor to receive more information regarding
what happened internal to the TaskQueueManager and strategy, to determine
things like whether or not the play iteration should stop.

Fixes #15523

lib/ansible/executor/task_queue_manager.py

@@ -58,6 +58,13 @@ class TaskQueueManager:
     which dispatches the Play's tasks to hosts.
     '''
 
+    RUN_OK                = 0
+    RUN_ERROR             = 1
+    RUN_FAILED_HOSTS      = 2
+    RUN_UNREACHABLE_HOSTS = 3
+    RUN_FAILED_BREAK_PLAY = 4
+    RUN_UNKNOWN_ERROR     = 255
+
     def __init__(self, inventory, variable_manager, loader, options, passwords, stdout_callback=None, run_additional_callbacks=True, run_tree=False):
 
         self._inventory        = inventory