test: add painter widget e2e tests (#10599)

## Summary
add painter widget e2e tests

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10599-test-add-painter-widget-e2e-tests-3306d73d365081899b3ec3e1d7c6f57c)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

browser_tests/assets/widgets/painter_widget.json

@@ -0,0 +1,48 @@
+{
+  "last_node_id": 1,
+  "last_link_id": 0,
+  "nodes": [
+    {
+      "id": 1,
+      "type": "Painter",
+      "pos": [50, 50],
+      "size": [450, 550],
+      "flags": {},
+      "order": 0,
+      "mode": 0,
+      "inputs": [
+        {
+          "name": "image",
+          "type": "IMAGE",
+          "link": null
+        }
+      ],
+      "outputs": [
+        {
+          "name": "IMAGE",
+          "type": "IMAGE",
+          "links": null
+        },
+        {
+          "name": "MASK",
+          "type": "MASK",
+          "links": null
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "Painter"
+      },
+      "widgets_values": ["", 512, 512, "#000000"]
+    }
+  ],
+  "links": [],
+  "groups": [],
+  "config": {},
+  "extra": {
+    "ds": {
+      "offset": [0, 0],
+      "scale": 1
+    }
+  },
+  "version": 0.4
+}