feat(spanner): run E2E test over DirectPath (#3466)
feat(spanner): run E2E test over DirectPath (#3466)

Co-authored-by: Knut Olav Løite <62634d14bf6dff6edb4b7af974862bb227095f71@gmail.com>
Co-authored-by: Thiago Nunes <b6c64d1c36cf138d08564c65806d2244f083123a@google.com>
googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go