iOS Modules: separate main platform code from modules

Moved previously builtin modules 'GameCenter', 'AppStore', 'iCloud' to separate modules to be represented as plugin.
Modified 'ARKit' and 'Camera' to not be builtin into engine and work as plugin.
Changed platform code so it's not affected by the move.
Modified Xcode project file to remove parameters that doesn't make any effect.
Added basic '.gdip' plugin config file.

modules/arkit/arkit.gdip

@@ -0,0 +1,18 @@
+[config]
+name="ARKit"
+binary="arkit_lib.a"
+
+initialization="register_arkit_types"
+deinitialization="unregister_arkit_types"
+
+[dependencies]
+linked=[]
+embedded=[]
+system=["AVFoundation.framework", "ARKit.framework"]
+
+capabilities=["arkit"]
+
+files=[]
+
+[plist]
+NSCameraUsageDescription="Device camera is used for some functionality"

modules/arkit/arkit_module.cpp

@@ -1,5 +1,5 @@
 /*************************************************************************/
-/*  register_types.cpp                                                   */
+/*  arkit_module.cpp                                                     */
 /*************************************************************************/
 /*                       This file is part of:                           */
 /*                           GODOT ENGINE                                */
@@ -28,7 +28,7 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#include "register_types.h"
+#include "arkit_module.h"
 
 #include "arkit_interface.h"
 

modules/arkit/arkit_module.h

@@ -1,5 +1,5 @@
 /*************************************************************************/
-/*  register_types.h                                                     */
+/*  arkit_module.h                                                       */
 /*************************************************************************/
 /*                       This file is part of:                           */
 /*                           GODOT ENGINE                                */