[DOCS] Reformat release highlights as What's new. (#58074)

* [DOCS] Reformat release highlights as What's new.

* Removed line break.

docs/reference/index.asciidoc

@@ -12,6 +12,8 @@ include::../Versions.asciidoc[]
 
 include::intro.asciidoc[]
 
+include::release-notes/highlights.asciidoc[]
+
 include::getting-started.asciidoc[]
 
 include::setup.asciidoc[]
@@ -72,8 +74,6 @@ include::glossary.asciidoc[]
 
 include::rest-api/index.asciidoc[]
 
-include::release-notes/highlights.asciidoc[]
-
 include::migration/index.asciidoc[]
 
 include::release-notes.asciidoc[]

docs/reference/intro.asciidoc

@@ -1,7 +1,5 @@
 [[elasticsearch-intro]]
-= Elasticsearch introduction
-[partintro]
---
+== What is {es}?
 _**You know, for search (and analysis)**_
 
 {es} is the distributed search and analytics engine at the heart of
@@ -35,10 +33,9 @@ We’re continually amazed by the novel ways people use search. But whether
 your use case is similar to one of these, or you're using {es} to tackle a new
 problem, the way you work with your data, documents, and indices in {es} is
 the same.
---
 
 [[documents-indices]]
-== Data in: documents and indices
+=== Data in: documents and indices
 
 {es} is a distributed document store. Instead of storing information as rows of
 columnar data, {es} stores complex data structures that have been serialized
@@ -91,7 +88,7 @@ used at search time. When you query a full-text field, the query text undergoes
 the same analysis before the terms are looked up in the index.
 
 [[search-analyze]]
-== Information out: search and analyze
+=== Information out: search and analyze
 
 While you can use {es} as a document store and retrieve documents and their
 metadata, the real power comes from being able to easily access the full suite
@@ -107,7 +104,7 @@ or Ruby.
 
 [float]
 [[search-data]]
-=== Searching your data
+==== Searching your data
 
 The {es} REST APIs support structured queries, full text queries, and complex
 queries that combine the two. Structured queries are
@@ -132,7 +129,7 @@ third-party applications to interact with {es} via SQL.
 
 [float]
 [[analyze-data]]
-=== Analyzing your data
+==== Analyzing your data
 
 {es} aggregations enable you to build complex summaries of your data and gain
 insight into key metrics, patterns, and trends. Instead of just finding the
@@ -164,7 +161,7 @@ embroidery_ needles.
 
 [float]
 [[more-features]]
-==== But wait, there’s more
+===== But wait, there’s more
 
 Want to automate the analysis of your time-series data? You can use
 {ml-docs}/ml-overview.html[machine learning] features to create accurate
@@ -179,7 +176,7 @@ And the best part? You can do this without having to specify algorithms, models,
 or other data science-related configurations.
 
 [[scalability]]
-== Scalability and resilience: clusters, nodes, and shards
+=== Scalability and resilience: clusters, nodes, and shards
 ++++
 <titleabbrev>Scalability and resilience</titleabbrev>
 ++++
@@ -211,7 +208,7 @@ interrupting indexing or query operations.
 
 [float]
 [[it-depends]]
-=== It depends...
+==== It depends...
 
 There are a number of performance considerations and trade offs with respect
 to shard size and the number of primary shards configured for an index. The more
@@ -239,7 +236,7 @@ testing with your own data and queries].
 
 [float]
 [[disaster-ccr]]
-=== In case of disaster
+==== In case of disaster
 
 For performance reasons, the nodes within a cluster need to be on the same
 network. Balancing shards in a cluster across nodes in different data centers
@@ -259,7 +256,7 @@ secondary clusters are read-only followers.
 
 [float]
 [[admin]]
-=== Care and feeding
+==== Care and feeding
 
 As with any enterprise system, you need tools to secure, manage, and
 monitor your {es} clusters. Security, monitoring, and administrative features

docs/reference/release-notes/8.0.0-alpha1.asciidoc

@@ -1,6 +1,8 @@
 [[release-notes-8.0.0-alpha1]]
 == {es} version 8.0.0-alpha1
 
+coming[8.0.0]
+
 The changes listed below have been released for the first time in {es}
 8.0.0-alpha1.
 
@@ -25,4 +27,4 @@ all we need to do is to set `index.indexing.slowlog.threshold.index.debug` and
 `index.indexing.slowlog.threshold.index.trace` to `-1` {pull}57591[#57591]
 
 
-coming[8.0.0]
+

docs/reference/release-notes/highlights.asciidoc

@@ -1,13 +1,31 @@
 [[release-highlights]]
-= Release highlights
+== What's new in {minor-version}
 
-[partintro]
---
-This section summarizes the most important changes in each release. For the 
-full list, see <<es-release-notes>> and <<breaking-changes>>. 
+coming[{minor-version}]
 
-* <<release-highlights-8.0.0>>
+Here are the highlights of what's new and improved in {es} {minor-version}! 
+ifeval::["{release-state}"!="unreleased"]
+For detailed information about this release, see the 
+<<release-notes-{elasticsearch_version}, Release notes >>  and 
+<<breaking-changes-{minor-version}, Breaking changes>>.
+endif::[]
 
---
+// Add previous release to the list
+// Other versions: 
+// {ref-bare}/7.last/release-highlights.html[7.last] 
+// | {ref-bare}/8.0/release-highlights.html[8.0]
 
-include::highlights-8.0.0.asciidoc[]
+// Use the notable-highlights tag to mark entries that 
+// should be featured in the Stack Installation and Upgrade Guide:
+// tag::notable-highlights[] 
+// [discrete]
+// === Heading
+//
+// Description. 
+// end::notable-highlights[]
+
+// Omit the notable highlights tag for entries that only need to appear in the ES ref:
+// [float] 
+// === Heading
+//
+// Description.