Remove dead 'beats' code (elastic#53312)

Author: jakelandis

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/XPackClientPlugin.java

@@ -39,7 +39,6 @@
 import org.elasticsearch.xpack.core.action.XPackInfoAction;
 import org.elasticsearch.xpack.core.action.XPackUsageAction;
 import org.elasticsearch.xpack.core.analytics.AnalyticsFeatureSetUsage;
-import org.elasticsearch.xpack.core.beats.BeatsFeatureSetUsage;
 import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata;
 import org.elasticsearch.xpack.core.ccr.CCRFeatureSet;
 import org.elasticsearch.xpack.core.deprecation.DeprecationInfoAction;
@@ -477,8 +476,6 @@ public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
                 new NamedWriteableRegistry.Entry(XPackFeatureSet.Usage.class, XPackField.GRAPH, GraphFeatureSetUsage::new),
                 // logstash
                 new NamedWriteableRegistry.Entry(XPackFeatureSet.Usage.class, XPackField.LOGSTASH, LogstashFeatureSetUsage::new),
-                // beats
-                new NamedWriteableRegistry.Entry(XPackFeatureSet.Usage.class, XPackField.BEATS, BeatsFeatureSetUsage::new),
                 // ML - Custom metadata
                 new NamedWriteableRegistry.Entry(MetaData.Custom.class, "ml", MlMetadata::new),
                 new NamedWriteableRegistry.Entry(NamedDiff.class, "ml", MlMetadata.MlMetadataDiff::new),

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/XPackSettings.java

@@ -90,10 +90,6 @@ private XPackSettings() {
     public static final Setting<Boolean> LOGSTASH_ENABLED = Setting.boolSetting("xpack.logstash.enabled", true,
             Setting.Property.NodeScope);
 
-    /** Setting for enabling or disabling Beats extensions. Defaults to true. */
-    public static final Setting<Boolean> BEATS_ENABLED = Setting.boolSetting("xpack.beats.enabled", true,
-        Setting.Property.NodeScope);
-
     /**
      * Setting for enabling or disabling the index lifecycle extension. Defaults to true.
      */