[Rector] Skip refactor() delegating REMOVE_NODE to helper methods

[TomasVotruba]

NoIntegerRefactorReturnRule only scanned the refactor() body for NodeVisitor/NodeTraverser constants. When refactor() delegates the int return to private helper methods, its own body contains zero constants — the old $constantNames === [] branch then fell through and reported an error, even when every helper returned the allowed REMOVE_NODE.

Real-world false positive: Rector's own RemovePhpVersionIdCheckRector, whose refactor() delegates entirely to refactorConstFetch() / refactorSmaller() / etc., all returning NodeVisitor::REMOVE_NODE.

Fix

Scan the whole class for used traverser constants (refactor helpers included), and only report when an undesired constant (anything other than REMOVE_NODE) is actually present.

Before / after

// bad — helper uses DONT_TRAVERSE_CHILDREN, still flagged
public function refactor(Node $node): null|int
{
    return $this->doRefactor($node);
}
private function doRefactor(Node $node): null|int
{
    return NodeVisitor::DONT_TRAVERSE_CHILDREN;
}

// good — helper only returns REMOVE_NODE, now correctly skipped
public function refactor(Node $node): null|int
{
    return $this->doRefactor($node);
}
private function doRefactor(Node $node): null|int
{
    return NodeVisitor::REMOVE_NODE;
}