[WIP] Move unrelated editor cover code to the right place

Closes #4106, Closes #4103

- Moves the `.editor-close` styles to `post-settings-menu.scss`
- Renames everything that was `right-outlet` to `settings-menu`
It is in the wrong place. Will move.

It gets applies because the `&` at the end of the selector which appends any parent selector in place of the `&`. So the compiled selector would be

```css
@media (max-width: 400px) {
    body.settings-menu-expanded .notifications {
        transform: translate3d(100%, 0px, 0px);
    }
}
```