Extract control dependency rewiring out of PhaseIdealLoop::dominated_by() into separate method

PhaseIdealLoop::dominated_by() only works with If nodes being dominated. However, at some point, we want to replace the IfNode for a Template Assertion Predicate with a dedicated TemplateAssertionPredicateNode. To still be able to rewire the control dependencies in Loop Predication for a hoisted range check to the new TemplateAssertionPredicateNode, we can extract the rewiring part out of dominated_by() into a separate method and use that one instead.