Nest data stream scenarios (#2099)

Author: bmorelli25

reference/fleet/toc.yml

@@ -148,10 +148,11 @@ toc:
       - file: data-streams.md
         children:
           - file: data-streams-ilm-tutorial.md
-          - file: data-streams-scenario1.md
-          - file: data-streams-scenario2.md
-          - file: data-streams-scenario3.md
-          - file: data-streams-scenario4.md
+            children:
+              - file: data-streams-scenario1.md
+              - file: data-streams-scenario2.md
+              - file: data-streams-scenario3.md
+              - file: data-streams-scenario4.md
           - file: data-streams-pipeline-tutorial.md
           - file: data-streams-advanced-features.md
   - file: agent-command-reference.md
@@ -202,4 +203,4 @@ toc:
       - file: timestamp-processor.md
       - file: translate_sid-processor.md
       - file: truncate_fields-processor.md
-      - file: urldecode-processor.md
+      - file: urldecode-processor.md