message: Add an explicit copy constructor to Status.
diff: @@ -151,6 +151,8 @@ class Status {
  // Abseil-compatible constructor from an error and a message
  Status(absl::StatusCode code, absl::string_view error_message);
  + Status(const Status& other) = default;
  +
  Status& operator=(const Status& other);
  #ifndef TINK_USE_ABSL_STATUS
  