[7.2] Adds APM release highlights to Installation Upgrade Guide (#382)

Author: lcawl

docs/en/install-upgrade/breaking.asciidoc

@@ -29,9 +29,9 @@ Upgrade Assistant provides information about which {dfeeds} need to be updated.
 ++++
 
 This list summarizes the most important breaking changes in APM. 
-For the complete list, go to {apm-server-ref-70}/breaking-changes.html[APM Server 7.0 breaking changes].
+For the complete list, go to {apm-server-ref}/breaking-changes.html[APM Server breaking changes].
 
-//include::{apm-repo-dir}/apm-breaking-changes.asciidoc[tag=notable-v7-breaking-changes]
+include::{apm-repo-dir}/apm-breaking-changes.asciidoc[tag=notable-v7-breaking-changes]
 
 [[beats-breaking-changes]]
 === Beats breaking changes

docs/en/install-upgrade/highlights.asciidoc

@@ -4,10 +4,24 @@
 Each release brings new features and product improvements. This section
 highlights notable new features and enhancements in {version}.
 
+** <<apm-highlights,APM>>
 ** <<beats-highlights,Beats>>
 ** <<elasticsearch-highlights,{es}>>
 ** <<kibana-higlights,{kib}>>
 
+[[apm-highlights]]
+=== APM highlights
+++++
+<titleabbrev>APM</titleabbrev>
+++++
+
+This list summarizes the most important enhancements in APM.
+For the complete list, go to
+{apm-get-started-ref}/apm-release-notes.html[APM release highlights].
+
+include::{apm-repo-dir}/apm-release-notes.asciidoc[tag=notable-v72-highlights]
+
+
 [[beats-highlights]]
 === {beats} highlights
 ++++