[DOCS] Add abbreviated titles

Original commit: elastic/x-pack-elasticsearch@a4cf8a363f

docs/en/settings/ml-settings.asciidoc

@@ -1,6 +1,10 @@
 [role="xpack"]
 [[ml-settings]]
-=== Machine Learning Settings
+=== Machine Learning Settings in Elasticsearch
+++++
+<titleabbrev>Machine Learning Settings</titleabbrev>
+++++
+
 You do not need to configure any settings to use {ml}. It is enabled by default.
 
 [float]

docs/en/settings/monitoring-settings.asciidoc

@@ -1,6 +1,9 @@
 [role="xpack"]
 [[monitoring-settings]]
-===  Monitoring Settings
+===  Monitoring Settings in Elasticsearch
+++++
+<titleabbrev>Monitoring Settings</titleabbrev>
+++++
 
 Monitoring is enabled by default when you install {xpack}. You can configure
 these monitoring settings in the `elasticsearch.yml` file.

docs/en/settings/notification-settings.asciidoc

@@ -1,6 +1,9 @@
 [role="xpack"]
 [[notification-settings]]
-=== {watcher} Settings
+=== {watcher} Settings in Elasticsearch
+++++
+<titleabbrev>{watcher} Settings</titleabbrev>
+++++
 
 You configure `xpack.notification` settings in `elasticsearch.yml` to
 send set up {watcher} and send notifications via <<email-notification-settings, email>>,

docs/en/settings/security-settings.asciidoc

@@ -1,6 +1,9 @@
 [role="xpack"]
 [[security-settings]]
-=== Security Settings
+=== Security Settings in Elasticsearch
+++++
+<titleabbrev>Security Settings</titleabbrev>
+++++
 
 You configure `xpack.security` settings  to
 <<anonymous-access-settings, enable anonymous access>>