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.

platform/javascript/export/export_plugin.cpp

@@ -31,7 +31,6 @@
 #include "export_plugin.h"
 
 #include "core/config/project_settings.h"
-#include "editor/editor_node.h"
 
 Error EditorExportPlatformJavaScript::_extract_template(const String &p_template, const String &p_dir, const String &p_name, bool pwa) {
 	FileAccess *src_f = nullptr;