ui/cocoa: Remove the uses of full screen APIs

ui/cocoa: Remove the uses of full screen APIs

The detections of [NSView -enterFullScreen:] and
[NSView -exitFullScreen:] were wrong. A detection is coded as:
[NSView respondsToSelector:@selector(exitFullScreenModeWithOptions:)]
but it should be:
[NSView instancesRespondToSelector:@selector(exitFullScreenModeWithOptions:)]

Because of those APIs were not detected, ui/cocoa always falled
back to a borderless window whose frame matches the screen to
implement fullscreen behavior.

The code using [NSView -enterFullScreen:] and
[NSView -exitFullScreen:] will be used if you fix the detections,
but its behavior is undesirable; the full screen view stretches
the video, changing the aspect ratio, even if zooming is disabled.

This change removes the code as it does nothing good.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-Id: <20210220013138.51437-1-akihiko.odaki@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>