Editor: Cleanup some includes dependencies

Removes some unnecessary includes from `editor_node.h`, and instead add
those where they're used.

Removes unnecessary `editor_node.h` includes in various editor classes.

Renames `dynamicfont` to `dynamic_font` in a couple files.

Misc cleanup while jumping through that rabbit hole.

editor/editor_settings.h

@@ -31,15 +31,13 @@
 #ifndef EDITOR_SETTINGS_H
 #define EDITOR_SETTINGS_H
 
-#include "core/input/shortcut.h"
 #include "core/io/config_file.h"
 #include "core/io/resource.h"
-#include "core/object/class_db.h"
 #include "core/os/thread_safe.h"
-#include "core/string/translation.h"
-#include "editor/editor_paths.h"
 
 class EditorPlugin;
+class InputEvent;
+class Shortcut;
 
 class EditorSettings : public Resource {
 	GDCLASS(EditorSettings, Resource);