Tweak the ECS fields in DeprecatedMessage (#62855)

Backport of #62855. Follow-up to #61484.

Author: pugnascotia

x-pack/plugin/deprecation/qa/rest/src/javaRestTest/java/org/elasticsearch/xpack/deprecation/DeprecationHttpIT.java

@@ -277,8 +277,8 @@ public void testDeprecationMessagesCanBeIndexed() throws Exception {
                             hasKey("cluster.name"),
                             hasKey("cluster.uuid"),
                             hasKey("component"),
-                            hasEntry("data_stream.datatype", "deprecation"),
-                            hasEntry("data_stream.namespace", "elasticsearch"),
+                            hasEntry("data_stream.dataset", "deprecation.elasticsearch"),
+                            hasEntry("data_stream.namespace", "default"),
                             hasEntry("data_stream.type", "logs"),
                             hasEntry("ecs.version", "1.6"),
                             hasEntry("key", "deprecated_settings"),
@@ -293,8 +293,8 @@ public void testDeprecationMessagesCanBeIndexed() throws Exception {
                             hasKey("cluster.name"),
                             hasKey("cluster.uuid"),
                             hasKey("component"),
-                            hasEntry("data_stream.datatype", "deprecation"),
-                            hasEntry("data_stream.namespace", "elasticsearch"),
+                            hasEntry("data_stream.dataset", "deprecation.elasticsearch"),
+                            hasEntry("data_stream.namespace", "default"),
                             hasEntry("data_stream.type", "logs"),
                             hasEntry("ecs.version", "1.6"),
                             hasEntry("key", "deprecated_route"),

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/logging/EcsJsonLayout.java

@@ -58,8 +58,8 @@ protected String pattern(String type, String[] esMessageFields) {
         map.put("node.name", inQuotes("%node_name"));
         map.put("message", inQuotes("%notEmpty{%enc{%marker}{JSON} }%enc{%.-10000m}{JSON}"));
         map.put("data_stream.type", inQuotes("logs"));
-        map.put("data_stream.datatype", inQuotes("deprecation"));
-        map.put("data_stream.namespace", inQuotes("elasticsearch"));
+        map.put("data_stream.dataset", inQuotes("deprecation.elasticsearch"));
+        map.put("data_stream.namespace", inQuotes("default"));
         map.put("ecs.version", inQuotes(ECS_VERSION));
 
         for (String key : esMessageFields) {