Install/Upgrade Guide: Remove + redirect breaking changes pages (#2495)

Updates the Install/Upgrade Guide's [Breaking changes](https://www.elastic.co/guide/en/elastic-stack/current/elastic-stack-breaking-changes.html) pages to remove `include::[]` statements for breaking changes. Based on [team feedback](https://elastic.slack.com/archives/C0JF80CJZ/p1690577645566499) (internal link — sorry), these `include`s often break and are difficult to maintain.

Related changes:
- Removes child pages that contain `include`s from other books. Replaces the pages with links to the respective doc books.
- Adds redirects for the removed child pages.
- Adds Fleet/Elastic Agent and Enterprise Search to the list.
- Updates the Beats and Logstash links to point to breaking changes pages. Beats and Logstash rarely has breaking changes.

(cherry picked from commit 583fbef)

# Conflicts:
#	docs/en/install-upgrade/breaking.asciidoc

docs/en/install-upgrade/breaking.asciidoc

@@ -5,12 +5,14 @@ Before you upgrade, you must review the breaking changes for each product you
 use and make the necessary changes so your code is compatible with {version}.
 
 // tag::breaking-changes-links[]
-** <<apm-breaking-changes,APM {version} breaking changes>>
-** <<beats-breaking-changes,Beats {version} breaking changes>>
-** <<elasticsearch-breaking-changes,{es} {version} breaking changes>>
-** <<security-breaking-changes,{elastic-sec} {version} breaking changes>>
-** <<kibana-breaking-changes,Kibana {version} breaking changes>>
-** <<logstash-breaking-changes,{ls} {version} breaking changes>>
+** {apm-guide-ref}/apm-breaking.html[APM breaking changes]
+** {beats-ref}/breaking-changes.html[{beats} breaking changes]
+** {ref}/breaking-changes.html[{es} migration guide]
+** {security-guide}/release-notes.html[{elastic-sec} release notes]
+** {enterprise-search-ref}/release-notes-{version}.html[{ents} release notes]
+** {fleet-guide}/release-notes.html[{fleet} and {agent} release notes]
+** {kibana-ref}/release-notes.html[{kib} release notes]
+** {logstash-ref}/breaking-changes.html[{ls} breaking changes]
 // end::breaking-changes-links[]
 
 // tag::breaking-changes-admon[]
@@ -24,6 +26,7 @@ Upgrade Assistant provides information about which {dfeeds} need to be updated.
 ===============================
 // end::breaking-changes-admon[]
 
+<<<<<<< HEAD
 [[apm-breaking-changes]]
 === APM breaking changes
 ++++
@@ -96,3 +99,5 @@ the complete list, go to
 {logstash-ref}/breaking-changes.html[Logstash breaking changes].
 
 include::{ls-repo-dir}/static/breaking-changes-80.asciidoc[tag=notable-breaking-changes]
+=======
+>>>>>>> 583fbef1 (Install/Upgrade Guide: Remove + redirect breaking changes pages (#2495))

docs/en/install-upgrade/redirects.asciidoc

@@ -25,4 +25,40 @@ See the {observability-guide}/whats-new.html[Observability highlights] page for
 === Highlights
 
 This page no longer exists.
-Go to {estc-welcome}/new.html[Check out the latest from Elastic].
+Go to {estc-welcome}/new.html[Check out the latest from Elastic].
+
+[role="exclude",id="apm-breaking-changes"]
+=== APM breaking changes
+
+This page no longer exists.
+See {apm-guide-ref}/apm-breaking.html[APM breaking changes] instead.
+
+[role="exclude",id="beats-breaking-changes"]
+=== Beats breaking changes
+
+This page no longer exists.
+See {beats-ref}/breaking-changes.html[{beats} breaking changes] instead.
+
+[role="exclude",id="elasticsearch-breaking-changes"]
+=== {es} breaking changes
+
+This page no longer exists.
+See {ref}/breaking-changes.html[{es} migration guide] instead.
+
+[role="exclude",id="security-breaking-changes"]
+=== {elastic-sec} breaking changes
+
+This page no longer exists.
+See {security-guide}/release-notes.html[{elastic-sec} release notes] instead.
+
+[role="exclude",id="kibana-breaking-changes"]
+=== {kib} breaking changes
+
+This page no longer exists.
+See {kibana-ref}/release-notes.html[{kib} release notes] instead.
+
+[role="exclude",id="logstash-breaking-changes"]
+=== {ls} breaking changes
+
+This page no longer exists.
+See {logstash-ref}/breaking-changes.html[{ls} breaking changes] instead.