[DOCS] Overhaul snapshot and restore docs (#79081)

Makes several changes to consolidate snapshot and backup-related docs.

Highlights:

* Adds info about supported ESS snapshot repository types
* Adds docs for Kibana's Snapshot and Restore feature
* Combines tutorial pages related to taking and managing snapshots
* Consolidates explanations of the snapshot process
* Incorporates SLM into the snapshot tutorial
* Removes duplicate "back up a cluster" pages

docs/Versions.asciidoc

@@ -68,3 +68,7 @@ ifeval::["{source_branch}"=="7.x"]
 :apm-server-ref-v:     {apm-server-ref-m}
 :apm-overview-ref-v:   {apm-overview-ref-m}
 endif::[]
+
+// Max recommended snapshots in a snapshot repo.
+// Used in the snapshot/restore docs.
+:max-snapshot-count: 200

docs/plugins/repository-s3.asciidoc

@@ -215,9 +215,9 @@ include a port. For example, the endpoint may be `172.17.0.2` or
 `172.17.0.2:9000`. You may also need to set `s3.client.CLIENT_NAME.protocol` to
 `http` if the endpoint does not support HTTPS.
 
-https://minio.io[Minio] is an example of a storage system that provides an
+https://minio.io[MinIO] is an example of a storage system that provides an
 S3-compatible API. The `repository-s3` plugin allows {es} to work with
-Minio-backed repositories as well as repositories stored on AWS S3. Other
+MinIO-backed repositories as well as repositories stored on AWS S3. Other
 S3-compatible storage systems may also work with {es}, but these are not
 covered by the {es} test suite.
 

docs/reference/high-availability.asciidoc

@@ -21,12 +21,10 @@ to achieve high availability despite failures.
   to serve searches from nearby clients.
 
 * The last line of defence against data loss is to take
-  <<backup-cluster,regular snapshots>> of your cluster so that you can restore
-  a completely fresh copy of it elsewhere if needed.
+  <<snapshots-take-snapshot,regular snapshots>> of your cluster so that you can
+  restore a completely fresh copy of it elsewhere if needed.
 --
 
 include::high-availability/cluster-design.asciidoc[]
 
-include::high-availability/backup-cluster.asciidoc[]
-
 include::ccr/index.asciidoc[]

docs/reference/ilm/index.asciidoc

@@ -20,8 +20,8 @@ default policies are configured automatically.
 image:images/ilm/index-lifecycle-policies.png[]
 
 [TIP]
-To automatically back up your indices and manage snapshots,
-use <<getting-started-snapshot-lifecycle-management,snapshot lifecycle policies>>.
+To automatically back up your indices and manage snapshots, use
+<<automate-snapshots-slm,snapshot lifecycle policies>>.
 
 * <<overview-index-lifecycle-management>>
 * <<ilm-concepts>>

docs/reference/ilm/start-stop.asciidoc

@@ -9,7 +9,7 @@ You can stop {ilm} to suspend management operations for all indices.
 For example, you might stop {ilm} when performing scheduled maintenance or making
 changes to the cluster that could impact the execution of {ilm-init} actions.
 
-IMPORTANT: When you stop {ilm-init}, <<snapshot-lifecycle-management, {slm-init}>> 
+IMPORTANT: When you stop {ilm-init}, <<automate-snapshots-slm,{slm-init}>> 
 operations are also suspended. 
 No snapshots will be taken as scheduled until you restart {ilm-init}.
 In-progress snapshots are not affected.