perf: Use AppendMany for SortOrderTransformer/newResMapFromResourceSl…

…ice/appendAll

Append in a loop is very expensive, O(N*M). By using AppendMany we get closer to O(N+M)
instead.

api/resmap/factory.go

@@ -126,13 +126,8 @@ func (rmF *Factory) FromSecretArgs(
 func newResMapFromResourceSlice(
 	resources []*resource.Resource) (ResMap, error) {
 	result := New()
-	for _, res := range resources {
-		err := result.Append(res)
-		if err != nil {
-			return nil, err
-		}
-	}
-	return result, nil
+	err := result.AppendMany(resources...)
+	return result, err
 }
 
 // NewResMapFromRNodeSlice returns a ResMap from a slice of RNodes

api/resmap/reswrangler.go

@@ -485,12 +485,7 @@ func (m *resWrangler) AppendAll(other ResMap) error {
 
 // appendAll appends all the resources, error on Id collision.
 func (m *resWrangler) appendAll(list []*resource.Resource) error {
-	for _, res := range list {
-		if err := m.Append(res); err != nil {
-			return err
-		}
-	}
-	return nil
+	return m.AppendMany(list...)
 }
 
 // AbsorbAll implements ResMap.