The Home notification component now has a storybook file. This work was
extracted from the `snaps` branch, and was originally implemented in
PR #12860.
The storybook file was enhanced to include more stories demonstrating
each likely usage scenario.
* 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.