A hidden overlay was preventing interactions with the lower 356 pixels
in the popup view when there are zero notifications. It was also
preventing interactions with the 100 pixels above the notifications in
the case where there were two notifications, which obscured the `Send`
button.
The first problem was solved by ensuring the notification wrapper isn't
rendered when there are no notifications. The second problem was solved
by updating the notification wrapper style to avoid setting a height.
* Replace use of backup-notification with use of home notification
* Pin notifications relative to window
* Remove unneeded isRequired condition on some home.component properties
* Refactor rendering of home notifications
* UX for multiple notifications
* Adds dismissal to provider request notification.
* Fix test failures
The e2e tests have been updated to reference `home-notification`
classnames instead of the removed `background-notification`. The
active tab proptypes and default values were updated as well.