prepareFollowLocatorNameChangesIterator = async (host, locator) => {
  await null;
  const changesIterator = makeRefIterator(
    await E(host).followLocatorNameChanges(locator),
  );
  await takeCount(changesIterator, 1);
  return changesIterator;
}
Calls `host.followLocatorNameChanges()` for the specified locator, takes the first
value (i.e. the array of all existing names) from the iterator, and returns the iterator.

@param {any} host - An endo host.
@param {string} locator