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_data.cpp

@@ -31,11 +31,11 @@
 #include "editor_data.h"
 
 #include "core/config/project_settings.h"
-#include "core/io/dir_access.h"
 #include "core/io/file_access.h"
 #include "core/io/resource_loader.h"
 #include "editor/editor_node.h"
-#include "editor/editor_settings.h"
+#include "editor/editor_plugin.h"
+#include "editor/plugins/script_editor_plugin.h"
 #include "scene/resources/packed_scene.h"
 
 void EditorHistory::cleanup_history() {