CLONE - Upgrade test using a big data set with many users

Test requirements:

This test should be run using a big data set from a real site with many users (over 10,000) so we can spot more issues during the upgrade process.

Test steps:

1. Restore the big data set into a database.
2. Upgrade the site to the last major release.
3. Upgrade the site to the latest new release candidate.
4. Mention in a comment the time taken to upgrade plus any errors encountered.
5. Copy and paste stats about the site from the site registration screen into a comment.