Add support for querying by leaf-list content

The Executor engine provides the option to query elements based on their leafs. This means you can build query like: "give me all elements of list "nodes" which have their leaf "node-class" set to string "foo".

factory.querySubtree(InstanceIdentifier.create(Some.class))
            .extractChild(Nodes.class)
                .matching().leaf(Nodes::getNodeClass).valueEquals("foo").build();

If we change the leaf "node-class" to leaf-list "node-classes", the query would looke like:
"give me all elements of list "nodes" which contain strings "foo" and "bar" in their leaf-list "node-classes" "

factory.querySubtree(InstanceIdentifier.create(Some.class))
            .extractChild(Nodes.class)
                .matching().leaf(Nodes::getNodeClasses).contains(List.of("foo", "bar")).build();

Add support fot leafList.contains() matching.