This change generalises the notification bar rendering to allow
more complex content to be displayed.
Now you must provide the full HTML of the notification message
when using `<aio-notification>`.
Also you can control whether clicking the content triggers the
notification to close or not.
This will support the new notification specified in "Other Items : 3" of
[#24140](https://github.com/angular/angular/issues/24140#issuecomment-397480410)
PR Close#25020