Add RCN Mutator for require(...) Condition Negation

Why

We already have operator-level mutators (ROR, LOR, etc.), but we don’t have a mutator that flips the full require guard condition itself.

That mutation is useful for catching weak negative-path tests around validation and auth checks.

What

Add mutator RCN that negates the first require condition argument:

• require(x > 0 && x < 10) -> require(!(x > 0 && x < 10))
• require(msg.sender == owner, "not owner") -> require(!(msg.sender == owner), "not owner")

Follow-up

I already have a fix in progress for RCN (require(...) condition negation), and I will open that as a separate PR soon, so this scope stays clean.