Monitor json diagnostics printing cleanup

The 'events' and 'script' config values were defined for every monitor.
Removed the extra definitions and moved the variables to MXS_MONITOR.

MariaDBMonitor was printing config values a second time, they are
already printed by the caller.

Moved the events enum definition to the internal header since it's no longer
required by modules.

Added a default config setting "all" to 'events' to clarify that it enables
all events.

server/modules/monitor/mmmon/mmmon.cc

@@ -433,19 +433,6 @@ extern "C" MXS_MODULE* MXS_CREATE_MODULE()
         NULL, /* Thread finish. */
         {
             {"detect_stale_master", MXS_MODULE_PARAM_BOOL, "false"},
-            {
-                "script",
-                MXS_MODULE_PARAM_PATH,
-                NULL,
-                MXS_MODULE_OPT_PATH_X_OK
-            },
-            {
-                "events",
-                MXS_MODULE_PARAM_ENUM,
-                MXS_MONITOR_EVENT_DEFAULT_VALUE,
-                MXS_MODULE_OPT_NONE,
-                mxs_monitor_event_enum_values
-            },
             {MXS_END_MODULE_PARAMS}
         }
     };