[DOCS] Create top-level "Search your data" page (#56058) (#57463)

**Goal**

Create a top-level search section. This will let us clean up our search
API reference docs, particularly content from [`Request body search`][0].

**Changes**

* Creates a top-level `Search your data` page. This page is designed to
  house concept and tutorial docs related to search.

* Creates a `Run a search` page under `Search your data`. For now, This
  contains a basic search tutorial. The goal is to add content from
  [`Request body search`][0] to this in the future.

* Relocates `Long-running searches` and `Search across clusters` under
  `Search your data`. Increments several headings in that content.

* Reorders the top-level TOC to move `Search your data` higher. Also
  moves the `Query DSL`, `EQL`, and `SQL access` chapters immediately
  after.

Relates to #48194

[0]: https://www.elastic.co/guide/en/elasticsearch/reference/master/search-request-body.html

docs/reference/index.asciidoc

@@ -18,13 +18,17 @@ include::setup.asciidoc[]
 
 include::upgrade.asciidoc[]
 
-include::aggregations.asciidoc[]
+include::search/index.asciidoc[]
 
 include::query-dsl.asciidoc[]
 
-include::modules/cross-cluster-search.asciidoc[]
+ifdef::permanently-unreleased-branch[]
+include::eql/index.asciidoc[]
+endif::[]
 
-include::async-search.asciidoc[]
+include::sql/index.asciidoc[]
+
+include::aggregations.asciidoc[]
 
 include::scripting.asciidoc[]
 
@@ -42,12 +46,8 @@ ifdef::permanently-unreleased-branch[]
 
 include::autoscaling/index.asciidoc[]
 
-include::eql/index.asciidoc[]
-
 endif::[]
 
-include::sql/index.asciidoc[]
-
 include::monitoring/index.asciidoc[]
 
 include::frozen-indices.asciidoc[]

docs/reference/modules/cross-cluster-search.asciidoc

@@ -1,6 +1,5 @@
-[chapter]
 [[modules-cross-cluster-search]]
-= Search across clusters
+== Search across clusters
 
 *{ccs-cap}* lets you run a single search request against one or more
 <<modules-remote-clusters,remote clusters>>. For example, you can use a {ccs} to
@@ -10,7 +9,7 @@ IMPORTANT: {ccs-cap} requires <<modules-remote-clusters, remote clusters>>.
 
 [float]
 [[ccs-supported-apis]]
-== Supported APIs
+=== Supported APIs
 
 The following APIs support {ccs}:
 
@@ -21,11 +20,11 @@ The following APIs support {ccs}:
 
 [float]
 [[ccs-example]]
-== {ccs-cap} examples
+=== {ccs-cap} examples
 
 [float]
 [[ccs-remote-cluster-setup]]
-=== Remote cluster setup
+==== Remote cluster setup
 
 To perform a {ccs}, you must have at least one remote cluster configured.
 
@@ -64,7 +63,7 @@ PUT _cluster/settings
 
 [float]
 [[ccs-search-remote-cluster]]
-=== Search a single remote cluster
+==== Search a single remote cluster
 
 The following <<search-search,search>> API request searches the
 `twitter` index on a single remote cluster, `cluster_one`.
@@ -133,7 +132,7 @@ The API returns the following response:
 
 [float]
 [[ccs-search-multi-remote-cluster]]
-=== Search multiple remote clusters
+==== Search multiple remote clusters
 
 The following <<search,search>> API request searches the `twitter` index on
 three clusters:
@@ -232,7 +231,7 @@ means the document came from the local cluster.
 
 [float]
 [[skip-unavailable-clusters]]
-== Skip unavailable clusters
+=== Skip unavailable clusters
 
 By default, a {ccs} returns an error if *any* cluster in the request is
 unavailable.
@@ -259,7 +258,7 @@ include matching documents from that cluster in the final results.
 
 [discrete]
 [[ccs-gateway-seed-nodes]]
-== Selecting gateway and seed nodes in sniff mode
+=== Selecting gateway and seed nodes in sniff mode
 
 For remote clusters using the <<sniff-mode,sniff connection>> mode, gateway and
 seed nodes need to be accessible from the local cluster via your network.
@@ -274,7 +273,7 @@ wanted, the seed nodes for a cluster can be a subset of these gateway nodes.
 
 [discrete]
 [[ccs-proxy-mode]]
-== {ccs} in proxy mode
+=== {ccs} in proxy mode
 
 <<proxy-mode,Proxy mode>> remote cluster connections support {ccs}. All remote
 connections connect to the configured `proxy_address`. Any desired connection
@@ -283,7 +282,7 @@ be implemented by the intermediate proxy at this configured address.
 
 [discrete]
 [[ccs-network-delays]]
-== How {ccs} handles network delays
+=== How {ccs} handles network delays
 
 Because {ccs} involves sending requests to remote clusters, any network delays
 can impact search speed. To avoid slow searches, {ccs} offers two options for
@@ -309,7 +308,7 @@ See <<ccs-unmin-roundtrips>> to learn how this option works.
 
 [discrete]
 [[ccs-min-roundtrips]]
-=== Minimize network roundtrips
+==== Minimize network roundtrips
 
 Here's how {ccs} works when you minimize network roundtrips.
 
@@ -335,7 +334,7 @@ image:images/ccs/ccs-min-roundtrip-client-response.svg[]
 
 [discrete]
 [[ccs-unmin-roundtrips]]
-=== Don't minimize network roundtrips
+==== Don't minimize network roundtrips
 
 Here's how {ccs} works when you don't minimize network roundtrips.
 

docs/reference/search/index.asciidoc

@@ -0,0 +1,39 @@
+[[search-your-data]]
+= Search your data
+
+[partintro]
+--
+
+[[search-query]]
+A _search query_, or _query_, is a request for information about data in one or
+more {es} indices.
+
+You can think of a query as a question, written in a way {es} understands.
+Depending on your data, you can use a query to get answers to questions like:
+
+* What pages on my website contain a specific word or phrase?
+* What processes on my server take longer than 500 milliseconds to respond?
+* What users on my network ran `regsvr32.exe` within the last week?
+* How many of my products have a price greater than $20? 
+
+A _search_ consists of one or more queries that are combined and sent to {es}.
+Documents that match the a search's queries are returned in the _hits_, or
+_search results_, of the response.
+
+A search may also contain additional information used to better process its
+queries. For example, a search may be limited to a specific index or only return
+a specific number of results.
+
+[discrete]
+[[search-toc]]
+=== In this section
+
+* <<run-a-search>>
+* <<modules-cross-cluster-search>>
+* <<async-search-intro>>
+
+--
+
+include::run-a-search.asciidoc[]
+include::{es-repo-dir}/async-search.asciidoc[]
+include::{es-repo-dir}/modules/cross-cluster-search.asciidoc[]