Coordinate systems

While doing https://github.com/rust-windowing/winit/pull/3890, I reviewed all our instances of [Physical|Logical|]Position, and categorized them relative to their origin point:

Desktop coordinates:

• MonitorHandle::position
• WindowEvent::Moved
• Window::outer_position/Window::set_outer_position

Window coordinates:

• Window::surface_position
• Window::set_cursor_position
• WindowEvent::Pointer*.position (from https://github.com/rust-windowing/winit/pull/3876) (maybe?)
• WindowEvent::Drag*.position (from https://github.com/rust-windowing/winit/pull/4079) (maybe?)

Surface coordinates:

• Window::set_ime_cursor_area
• Window::show_window_menu

MouseScrollDelta::PixelDelta is a delta, so it has no origin and hence no coordinate system.

I believe that we should make set_cursor_position, WindowEvent::Pointer*.position and WindowEvent::Drag*.position use surface coordinates, since that's the easier coordinate system for users to work with.

Start by reviewing the coordinate categories and API references in this issue, then read pull requests 3890, 3876, and 4079 for the related position behavior. Check how set_cursor_position, WindowEvent::Pointer*.position, and WindowEvent::Drag*.position are currently defined. Done means their coordinate origins are decided and documented consistently with the other listed APIs.