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/android/export/export.cpp

@@ -32,6 +32,9 @@
 
 #include "export_plugin.h"
 
+#include "core/os/os.h"
+#include "editor/editor_settings.h"
+
 void register_android_exporter() {
 	String exe_ext;
 	if (OS::get_singleton()->get_name() == "Windows") {