Show notifications always on the top window

[varjolintu]

If a notification is shown inside an iframe, it's highly possible that it will be partially cut off, or is displayed in strange position. If kpxcUI.createNotification() is called inside an iframe, pass the message to the top window and show it there instead.

• Fixes #2255

Testing strategy

Any site with login form inside an iframe, e.g. https://mail.163.com/ or https://issues.imfreedom.org/projects. Just don't have any entries for it, and click the Username Icon.

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[droidmonkey]

This will be a very welcome change.