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/debugger/script_editor_debugger.h

@@ -39,7 +39,6 @@
 #include "scene/gui/margin_container.h"
 
 class Tree;
-class EditorNode;
 class LineEdit;
 class TabContainer;
 class RichTextLabel;