cocoa_common: override core's cursor visibility state

This keeps the state in sync with the current state in cocoa_common. Infact the
cocoa code in mpv can decide wether it really wants to hide the cursor based on
the result of the `canHideCursor` method (this is so that the cursor is only
hidden when hovering on the video window).
cocoa_common: signal a mouse movement when changing window size

This is mainly to avoid spurious cursor states due to the mouse moving inside
or outside the window as a result of the window resize (with cmd-0/1/2).

This avoids complex logic and triggers a mouse move so that the player
recomputes the correct cursor state based on the autohide configuration of
the user.