split create_binary into two phases

Which gives instructions a chance to check everything
and in Arms case check the constant loads/ instruction adding
So that during assembly no more change happens (and we don't have to reassemble)

test/risc/test_translator.rb

@@ -33,7 +33,7 @@ module Risc
       @machine.object_positions.keys.each do |method|
         next unless method.is_a? Parfait::TypedMethod
         method.cpu_instructions.each do |ins|
-          ins.assemble(DevNull.new)
+          ins.assemble(Util::DevNull.new)
         end
       end
     end