cleanup(spanner): pass argv to run-once commands by (moved) value (#6550)
cleanup(spanner): pass argv to run-once commands by (moved) value (#6550)

This will allow for sample commands that want to modify `argv`,
by consuming options for example, before using the argument values.
googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp