Finishes #378
Supercedes #4159
This adds a new enum value for `macos-non-native-fullscreen`:
`padded-notch`. This value will add padding to the top of the window to
account for the notch on applicable devices while still hiding the
menu.
This value is preferred over "visible-menu" by some people because for
screens without a notch, the window will take up the full height.
The plan in the future is that we may color the padded area when a notch
is present. In this commit it appears as transparent.