Include following chagnes to custom widget plugin

1. removed unsupported methods
2. auto-generate providerId
3. piggy-back context for the plugin to resolve resources

Bug: 139888225
Change-Id: If5014099eb80efd64025230037aae3d6079b69a0

src_plugins/com/android/systemui/plugins/CustomWidgetPlugin.java

@@ -29,28 +29,11 @@ public interface CustomWidgetPlugin extends Plugin {
     String ACTION = "com.android.systemui.action.PLUGIN_CUSTOM_WIDGET";
     int VERSION = 1;
 
-    /**
-     * An unique identifier for this widget. Must be a non-negative integer.
-     */
-    int getProviderId();
-
     /**
      * The label to display to the user in the AppWidget picker.
      */
     String getLabel();
 
-    /**
-     * A preview of what the AppWidget will look like after it's configured.
-     * If not supplied, the AppWidget's icon will be used.
-     */
-    int getPreviewImage();
-
-    /**
-     * The icon to display for this AppWidget in the AppWidget picker. If not supplied in the
-     * xml, the application icon will be used.
-     */
-    int getIcon();
-
     /**
      * The default width of the widget when added to a host, in dp. The widget will get
      * at least this width, and will often be given more, depending on the host.