check for pagination stopOnSameToken option

[kuhe]

aws/aws-sdk-js-v3#3490

Add check for optional pagination halt condition of prevToken equalling nextToken.

In test output:

    const prevToken = token;
    token = page.nextToken;
    hasNext = !!(token && (!config.stopOnSameToken || token !== prevToken));

This depends on aws/aws-sdk-js-v3#3524