add helper to iterate over elements of an addrs map

internal/addrs/map.go

@@ -3,6 +3,8 @@
 
 package addrs
 
+import "iter"
+
 // Map represents a mapping whose keys are address types that implement
 // UniqueKeyer.
 //
@@ -135,3 +137,13 @@ func (m Map[K, V]) Values() []V {
 	}
 	return ret
 }
+
+func (m Map[K, V]) Iter() iter.Seq2[K, V] {
+	return func(yield func(K, V) bool) {
+		for _, elem := range m.Elements() {
+			if !yield(elem.Key, elem.Value) {
+				return
+			}
+		}
+	}
+}