For T414370, we need to transition ~200k users from a hidden experiment preference (readinglists-web-ui-enabled) to the beta feature preference (readinglistsbeta).

This task involves adding the capability to duplicate a user preference (user option), e.g. set new option for all users with some particular current option.

To make this simple, add a one-off script setBetaPreference.php for this purpose.

Modifying the userOptions.php script in core is more involved, as the script does a lot already and we would need to be careful not to break any existing functionality there.

See T414370