Merged PR 320270: Add support of registering external components to SDK

Add support of registering external components to SDK

How does it work?
1. User creates a new embed component extending `Embed` in his project
2. User implements the necessary code in FE to support hosting of the new component and handling events
3. Needed code to embed the new component:
`powerbi.register(componentType, embedComponentFactory, routerEventUrls);`
`powerbi.embed(embedContainer, config);`

powerbi.register:
- `componentType`: string representing the component type in embed configuration interface
- `embedComponentFactory`: function that returns a new instance of the embed component.
- `routerEventUrls`: list of urls to register, must use uniqueId and eventName as keys. something like that: `/componentName/:uniqueId/events/:eventName`

Example of calling powerbi.register for metric-picker  component:

```
    this.register(
      'metric_picker',
      (service, element, config, phasedRender, isBootstrap) => new MetricPicker(service, element, config, phasedRender, isBootstrap),
      ['/metricPicker/:uniqueId/events/:eventName']
    );
```

Author: Or Shemesh

dist/powerbi-client.d.ts

@@ -2137,6 +2137,10 @@ declare module "service" {
         hpm: HttpPostMessage;
     }
     export type IComponentEmbedConfiguration = IReportEmbedConfiguration | IDashboardEmbedConfiguration | ITileEmbedConfiguration | IVisualEmbedConfiguration | IQnaEmbedConfiguration;
+    /**
+     * @hidden
+     */
+    export type EmbedComponentFactory = (service: Service, element: HTMLElement, config: IEmbedConfigurationBase, phasedRender?: boolean, isBootstrap?: boolean) => Embed;
     /**
      * The Power BI Service embed component, which is the entry point to embed all other Power BI components into your application
      *
@@ -2162,7 +2166,7 @@ declare module "service" {
         accessToken: string;
         /** The Configuration object for the service*/
         private config;
-        /** A list of Dashboard, Report and Tile components that have been embedded using this service instance. */
+        /** A list of Power BI components that have been embedded using this service instance. */
         private embeds;
         /** TODO: Look for way to make hpm private without sacrificing ease of maintenance. This should be private but in embed needs to call methods.
          *
@@ -2176,6 +2180,10 @@ declare module "service" {
         wpmp: WindowPostMessageProxy;
         router: Router;
         private uniqueSessionId;
+        /**
+         * @hidden
+         */
+        private registeredComponents;
         /**
          * Creates an instance of a Power BI Service.
          *
@@ -2257,10 +2265,25 @@ declare module "service" {
          * @private
          * @param {IPowerBiElement} element
          * @param {IEmbedConfigurationBase} config
+         * @param {boolean} phasedRender
+         * @param {boolean} isBootstrap
          * @returns {Embed}
          * @hidden
          */
         private embedNew;
+        /**
+         * Given component type, creates embed component instance
+         *
+         * @private
+         * @param {string} componentType
+         * @param {HTMLElement} element
+         * @param {IEmbedConfigurationBase} config
+         * @param {boolean} phasedRender
+         * @param {boolean} isBootstrap
+         * @returns {Embed}
+         * @hidden
+         */
+        private createEmbedComponent;
         /**
          * Given an element that already contains an embed component, load with a new configuration.
          *
@@ -2345,6 +2368,15 @@ declare module "service" {
          * @returns {void}
          */
         setSdkInfo(type: string, version: string): void;
+        /**
+         * API for registering external components
+         *
+         * @hidden
+         * @param {string} componentType
+         * @param {EmbedComponentFactory} embedComponentFactory
+         * @param {string[]} routerEventUrls
+         */
+        register(componentType: string, embedComponentFactory: EmbedComponentFactory, routerEventUrls: string[]): void;
     }
 }
 declare module "bookmarksManager" {