[api-minor] Render pushbuttons on their own canvas (bug 1737260)

- First step to fix https://bugzilla.mozilla.org/show_bug.cgi?id=1737260;
 - several interactive pdfs use the possibility to hide/show buttons to show different icons;
 - render pushbuttons on their own canvas and then insert it the annotation_layer;
 - update test/driver.js in order to convert canvases for pushbuttons into images.

web/interfaces.js

@@ -175,6 +175,8 @@ class IPDFAnnotationLayerFactory {
    * @param {Object} [mouseState]
    * @param {Promise<Object<string, Array<Object>> | null>}
    *   [fieldObjectsPromise]
+   * @property {Map<string, Canvas> | null} [annotationCanvasMap] - Map some
+   *  annotation ids with canvases used to render them.
    * @returns {AnnotationLayerBuilder}
    */
   createAnnotationLayerBuilder(
@@ -187,7 +189,8 @@ class IPDFAnnotationLayerFactory {
     enableScripting = false,
     hasJSActionsPromise = null,
     mouseState = null,
-    fieldObjectsPromise = null
+    fieldObjectsPromise = null,
+    annotationCanvasMap = null
   ) {}
 }