[api-minor] Deprecate getGlobalEventBus and update the "viewer components" examples accordingly

To avoid outright breaking third-party usages of the "viewer components" the `getGlobalEventBus` functionality is left intact, but a deprecation message is printed if the function is invoked.

The various examples are updated to *explicitly* initialize an `EventBus` instance, and provide that when initializing the relevant viewer components.

web/pdf_page_view.js

@@ -444,7 +444,8 @@ class PDFPageView {
         textLayerDiv,
         this.id - 1,
         this.viewport,
-        this.textLayerMode === TextLayerMode.ENABLE_ENHANCE
+        this.textLayerMode === TextLayerMode.ENABLE_ENHANCE,
+        this.eventBus
       );
     }
     this.textLayer = textLayer;