Add assertion the sizes of the sets are equal

This commit addresses #3859 (comment)

aws/sdk/integration-tests/ec2/tests/paginators.rs

@@ -22,6 +22,7 @@ fn validate_query_string(expected: &str, actual: &str) {
  let expected = expected.split('&').collect::<HashSet<&str>>();
  let actual = actual.split('&').collect::<HashSet<&str>>();
  assert_eq!(expected, actual);
+ assert_eq!(expected.len(), actual.len());
 }
 
 /// See https://github.com/awslabs/aws-sdk-rust/issues/391