[Truffle] We should always use the logical class newInstance for #dup and #clone.
[Truffle] Implement initialize_copy for String.
[Truffle] Implement Array#initialize_copy.
[Truffle] Implement Hash#initialize_copy.
[Truffle] Sort HashNodes.
[Truffle] Inline helper methods since we have only 1 specialization.
[Truffle] Copy over the singleton class in Kernel#clone.

* Fixes the last failing specs of singleton_class/metaclass.