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_export.cpp

@@ -45,6 +45,7 @@
 #include "core/version.h"
 #include "editor/editor_file_system.h"
 #include "editor/editor_node.h"
+#include "editor/editor_paths.h"
 #include "editor/editor_settings.h"
 #include "editor/plugins/script_editor_plugin.h"
 #include "scene/resources/resource_format_text.h"