Call interpreter.copyOperation consistently

Before this change, `Frame.execute` did not invoke the interpreter's
`copyOperation` method for all values that are pushed on the frame's
when executing some copying instructions.

For example, in the case of `SWAP`, `copyOperation` is invoked:

    value2 = pop();
    value1 = pop();
    push(interpreter.copyOperation(insn, value2));
    push(interpreter.copyOperation(insn, value1));

For `DUP` on the other hand, the original value is pushed onto the
stack without notifying the interpreter:

    value1 = pop();
    push(interpreter.copyOperation(insn, value1));

This leads to a problem for the `SourceInterpreter`, which collects
for every value a set of potential producer instructions. Given the
bytecode sequence

    NEW java/lang/Object
    INVOKESPECIAL java/lang/Object.<init> ()V

In the frame of the `INVOKESPECIAL` instruction, the value on the stack
lists as its producer the `NEW` operation instead of the `DUP`, which
not expected.
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