topology: add for_each_node

To eventually replace token_metadata::get_endpoint_to_host_id_map_for_reading

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>

locator/topology.cc

@@ -495,6 +495,14 @@ std::weak_ordering topology::compare_endpoints(const inet_address& address, cons
     return d1 <=> d2;
 }
 
+void topology::for_each_node(std::function<void(const node*)> func) const {
+    for (const auto& np : _nodes) {
+        if (np) {
+            func(np.get());
+        }
+    }
+}
+
 } // namespace locator
 
 namespace std {

locator/topology.hh

@@ -250,6 +250,8 @@ public:
      */
     void sort_by_proximity(inet_address address, inet_address_vector_replica_set& addresses) const;
 
+    void for_each_node(std::function<void(const node*)> func) const;
+
 private:
     // default constructor for cloning purposes
     topology() noexcept;