mac/view: fix cursor visibility when toggling fullscreen

this broke with the recent refactor of the input handling. one of the
edge cases was not considered, where not every mouse down event has a
corresponding mouse up event, eg all double clicks or more only have one
up event after the first down event.

this was handled correctly previously.

Fixes mpv-player#13777

video/out/mac/view.swift

@@ -134,7 +134,7 @@ class View: NSView, CALayerDelegate {
     }
 
     override func mouseDown(with event: NSEvent) {
-        hasMouseDown = true
+        hasMouseDown = event.clickCount <= 1
         input?.processMouse(event: event)
     }
 
@@ -145,7 +145,7 @@ class View: NSView, CALayerDelegate {
     }
 
     override func rightMouseDown(with event: NSEvent) {
-        hasMouseDown = true
+        hasMouseDown = event.clickCount <= 1
         input?.processMouse(event: event)
     }
 
@@ -155,7 +155,7 @@ class View: NSView, CALayerDelegate {
     }
 
     override func otherMouseDown(with event: NSEvent) {
-        hasMouseDown = true
+        hasMouseDown = event.clickCount <= 1
         input?.processMouse(event: event)
     }