[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.

src/core/document.js

@@ -407,6 +407,7 @@ class Page {
                 .getOperatorList(
                   partialEvaluator,
                   task,
+                  intent,
                   renderForms,
                   annotationStorage
                 )