Add snapshots to important config list (#65338)

The _Important Elasticsearch configuration_ docs lists a number of items
that you should consider before moving to production. Today this list
does not include configuring snapshots, even though they're very
important to have in production. This commit addresses that omission,
removes some repetition from the introductory paragraphs, and notes that
this config is handled for you on Cloud.

Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com>

docs/reference/setup/important-settings.asciidoc

@@ -1,10 +1,8 @@
 [[important-settings]]
 == Important Elasticsearch configuration
 
-While Elasticsearch requires very little configuration, there are a number of
-settings which need to be considered before going into production.
-
-The following settings *must* be considered before going to production:
+{es} requires very little configuration to get started, but there are a number
+of items which *must* be considered before using your cluster in production:
 
 * <<path-settings,Path settings>>
 * <<cluster-name,Cluster name setting>>
@@ -16,6 +14,10 @@ The following settings *must* be considered before going to production:
 * <<gc-logging,GC logging settings>>
 * <<es-tmpdir,Temporary directory settings>>
 * <<error-file-path,JVM fatal error log setting>>
+* <<important-settings-backups,Cluster backups>>
+
+Our {ess-trial}[{ecloud}] service configures these items automatically, making
+your cluster production-ready by default.
 
 include::important-settings/path-settings.asciidoc[]
 
@@ -36,3 +38,5 @@ include::important-settings/gc-logging.asciidoc[]
 include::important-settings/es-tmpdir.asciidoc[]
 
 include::important-settings/error-file.asciidoc[]
+
+include::important-settings/snapshot.asciidoc[]

docs/reference/setup/important-settings/snapshot.asciidoc

@@ -0,0 +1,9 @@
+[[important-settings-backups]]
+[discrete]
+=== Cluster backups
+
+In a disaster, <<snapshot-restore,snapshots>> can prevent permanent data loss.
+<<snapshot-lifecycle-management,{slm-cap}>> is the easiest way to take regular
+backups of your cluster. For more information, see <<backup-cluster>>.
+
+include::../../snapshot-restore/index.asciidoc[tag=backup-warning]