Minimize include dependencies of display_server.h

- Removes `native_menu.h` dependency from `display_server.h`.
  It's now forward-declared in all DisplayServer implementations and should
  be included in the .cpp's.
- Removes some unused `rb_set.h` and `rb_map.h` dependencies, which leads to
  having to include them explicitly in half the scene and editor codebase...
  which shows how much we depend on `display_server.h`.
- Forward-declare `input_event.h`, so now we need only `keyboard.h`.

drivers/apple_embedded/display_server_apple_embedded.h

@@ -30,7 +30,6 @@
 
 #pragma once
 
-#include "core/input/input.h"
 #include "servers/display/display_server.h"
 
 #if defined(RD_ENABLED)
@@ -55,6 +54,9 @@
 #import <Foundation/Foundation.h>
 #import <QuartzCore/CAMetalLayer.h>
 
+class InputEvent;
+class NativeMenu;
+
 class DisplayServerAppleEmbedded : public DisplayServer {
 	GDSOFTCLASS(DisplayServerAppleEmbedded, DisplayServer);
 

drivers/apple_embedded/display_server_apple_embedded.mm

@@ -40,7 +40,9 @@
 #import "tts_apple_embedded.h"
 
 #include "core/config/project_settings.h"
+#include "core/input/input.h"
 #include "core/io/file_access_pack.h"
+#include "servers/display/native_menu.h"
 
 #import <GameController/GameController.h>
 

drivers/vulkan/rendering_device_driver_vulkan.h

@@ -32,6 +32,7 @@
 
 #include "core/templates/hash_map.h"
 #include "core/templates/paged_allocator.h"
+#include "core/templates/rb_map.h"
 #include "drivers/vulkan/rendering_context_driver_vulkan.h"
 #include "drivers/vulkan/rendering_shader_container_vulkan.h"
 #include "servers/rendering/rendering_device_driver.h"