Re-implement the event generator as a new-style plugin - Mct4552 (#4620)

Updates Event Generator to ES6 classes and current API.

Co-authored-by: Andrew Henry <akhenry@gmail.com>
Co-authored-by: John Hill <john.c.hill@nasa.gov>

example/eventGenerator/EventMetadataProvider.js

@@ -0,0 +1,64 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2022, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT is licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * Open MCT includes source code licensed under additional open source
+ * licenses. See the Open Source Licenses file (LICENSES.md) included with
+ * this source code distribution or the Licensing information page available
+ * at runtime from the About dialog for additional information.
+ *****************************************************************************/
+
+class EventMetadataProvider {
+    constructor() {
+        this.METADATA_BY_TYPE = {
+            'eventGenerator': {
+                values: [
+                    {
+                        key: "name",
+                        name: "Name",
+                        format: "string"
+                    },
+                    {
+                        key: "utc",
+                        name: "Time",
+                        format: "utc",
+                        hints: {
+                            domain: 1
+                        }
+                    },
+                    {
+                        key: "message",
+                        name: "Message",
+                        format: "string"
+                    }
+                ]
+            }
+        };
+    }
+
+    supportsMetadata(domainObject) {
+        return Object.prototype.hasOwnProperty.call(this.METADATA_BY_TYPE, domainObject.type);
+    }
+
+    getMetadata(domainObject) {
+        return Object.assign(
+            {},
+            domainObject.telemetry,
+            this.METADATA_BY_TYPE[domainObject.type]
+        );
+    }
+}
+
+export default EventMetadataProvider;