Protect against very large stdout fields

* Defer loading result_stdout_text until specifically needed
* Conditionally display it based on the size of the field
* Provide a helpful message otherwise

awx/settings/defaults.py

@@ -562,6 +562,8 @@ FACT_CACHE_PORT = 6564
 
 ORG_ADMINS_CAN_SEE_ALL_USERS = True
 
+STDOUT_MAX_BYTES_DISPLAY = 1000000
+
 # Logging configuration.
 LOGGING = {
     'version': 1,