Add backend tests for unsupported_dialog_without_watch
Ensure the unsupported_dialog and cookies_disabled screens show without the loading screen.

Ensure the styling of the unsupported_dialog and cookies_disabled screens match other parts of the site. (vertically centered error messages)

fixes #3783
fixes #3784
Prevent the loading screen from being shown on unsupported_dialog_without_watch
That was embarrassing. The last `showLoading: true` should have been false.
Update unsupported_dialog_without_watch.ejs

Rewrote message to focus on user error first, and developer message second.
Slight update to the Unsupported without watch text.
Fix the error in the storage.js test.