Iterating over a InsnList with an iterator traverses the list twice

When you traverse an InsnList either with a for-each loop or explicitly with an iterator:

void iter(InsnList insns) {
    for(AbstractInsnNode insn : insns) { /* ... */ }
    // Or
    ListIterator<AbstractInsnNode> it = insns.iterator();
    while(it.hasNext()) {
        AbstractInsnNode insn = it.next();
        /* ... */
    }
}

The InsnList is traversed twice, as the call to InsnList.iterator() calls InsnList.get(0) internally, which populates the instruction cache by traversing the instruction list.

This is a waste of time and space if the cache is unneeded.

I'll happily submit a Merge Request unless there's a good reason that the implementation should stay as it is.