cocoa: remove OpenGL cocoa backend

the OpenGL cocoa backend was deprecated in 0.29, it has lot of bugs, is
completely unmaintained and can't properly playback anything anymore on
the newest macOS. it is time to remove it.

DOCS/interface-changes.rst

@@ -117,6 +117,7 @@ Interface changes
     - add `--target-gamut`
     - change the way display names are retrieved on macOS, usage of options and properties
       `--fs-screen-name`, `--screen-name` and `display-names` needs to be adjusted
+    - remove OpenGL cocoa backend that was deprecated in 0.29
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

meson.build

@@ -388,11 +388,7 @@ if features['cocoa']
                      'osdep/macosx_events.m',
                      'osdep/macosx_menubar.m',
                      'osdep/main-fn-cocoa.c',
-                     'osdep/path-macosx.m',
-                     'video/out/cocoa_common.m',
-                     'video/out/cocoa/events_view.m',
-                     'video/out/cocoa/video_view.m',
-                     'video/out/cocoa/window.m')
+                     'osdep/path-macosx.m')
 endif
 
 if posix
@@ -1079,7 +1075,6 @@ features += {'gl-cocoa': gl_cocoa.allowed()}
 if features['gl-cocoa']
     dependencies += GL
     features += {'gl': true}
-    sources += files('video/out/opengl/context_cocoa.c')
 endif
 
 gl_win32 = get_option('gl-win32').require(
@@ -1517,8 +1512,8 @@ if features['cocoa'] and features['swift']
 endif
 
 macos_cocoa_cb = get_option('macos-cocoa-cb').require(
-    features['cocoa'] and features['swift'],
-    error_message: 'Either cocoa or swift could not be found!',
+    features['cocoa'] and features['gl-cocoa'] and features['swift'],
+    error_message: 'Either cocoa, gl-cocoa or swift could not be found!',
 )
 features += {'macos-cocoa-cb': macos_cocoa_cb.allowed()}
 if features['macos-cocoa-cb']