Style: Harmonize header includes in platform ports

This applies our existing style guide, and adds a new rule to that style
guide for modular components such as platform ports and modules:

Includes from the platform port or module should be included with relative
paths (relative to the root folder of the modular component, e.g.
`platform/linuxbsd/`), in their own section before Godot's "core" includes.

The `api` and `export` subfolders also need to be handled as self-contained
(and thus use relative paths for their "local" includes) as they are all
compiled for each editor platform, without necessarily having the api/export
matching platform folder in the include path.
E.g. the Linux editor build will compile `platform/android/{api,export}/*.cpp`
and those need to use relative includes for it to work.

platform/macos/display_server_macos.h

@@ -31,8 +31,6 @@
 #ifndef DISPLAY_SERVER_MACOS_H
 #define DISPLAY_SERVER_MACOS_H
 
-#define BitMap _QDBitMap // Suppress deprecated QuickDraw definition.
-
 #include "core/input/input.h"
 #include "servers/display_server.h"
 
@@ -41,10 +39,13 @@
 #endif // GLES3_ENABLED
 
 #if defined(VULKAN_ENABLED)
+#include "vulkan_context_macos.h"
+
 #include "drivers/vulkan/rendering_device_vulkan.h"
-#include "platform/macos/vulkan_context_macos.h"
 #endif // VULKAN_ENABLED
 
+#define BitMap _QDBitMap // Suppress deprecated QuickDraw definition.
+
 #import <AppKit/AppKit.h>
 #import <AppKit/NSCursor.h>
 #import <ApplicationServices/ApplicationServices.h>