[DOCS] Adds breaking changes for 7.5 (#50416)

Author: gchaps

docs/migration.asciidoc

@@ -6,6 +6,7 @@
 This section discusses the changes that you need to be aware of when migrating
 your application from one version of Kibana to another.
 
+* <<breaking-changes-7.5, Breaking changes in 7.5>>
 * <<breaking-changes-7.4, Breaking changes in 7.4>>
 * <<breaking-changes-7.3, Breaking changes in 7.3>>
 * <<breaking-changes-7.2, Breaking changes in 7.2>>
@@ -15,6 +16,7 @@ your application from one version of Kibana to another.
 See also <<release-highlights>> and <<release-notes>>. 
 --
 
+include::migration/migrate_7_5.asciidoc[]
 include::migration/migrate_7_4.asciidoc[]
 include::migration/migrate_7_3.asciidoc[]
 include::migration/migrate_7_2.asciidoc[]

docs/migration/migrate_7_5.asciidoc

@@ -0,0 +1,32 @@
+[[breaking-changes-7.5]]
+== Breaking changes in 7.5
+++++
+<titleabbrev>7.5</titleabbrev>
+++++
+
+This page discusses the breaking changes that you need to be aware of when migrating
+your application to Kibana 7.5.
+
+//See also <<release-highlights-7.4.0, release highlights>> and <<release-notes-7.4.0, release notes>>.
+
+//NOTE: The notable-breaking-changes tagged regions are re-used in the
+//Installation and Upgrade Guide
+
+////
+The following section is re-used in the Installation and Upgrade Guide
+[[breaking_70_notable]]
+=== Notable breaking changes
+////
+// tag::notable-breaking-changes[]
+
+[float]
+[[breaking_75_search_instead_of-msearch]]
+=== The default setting for `courier:batchSearches` is now `false`
+
+*Details:*
+Changing the default setting for `courier:batchSearches` to `false` means 
+that search requests will use the `_search` {es} endpoint rather than `_msearch`. 
+
+*Impact:*
+Dashboard panels will load individually, and search requests will terminate 
+when users navigate away or update the query.