Allow championships to restrict advancement to competitors from the relevant region

[zhouyichen]

Is your feature request related to a problem? Please describe.
There is the new advancement condition in 2025, but currently not supported by the WCA websites.

Describe the solution you'd like
Please help to implement the necessary features to support this new advancement condition, which might include the WCA main website, WCA Live, WCIF etc.

Describe alternatives you've considered
Worst case if the features could not be implemented in time, we could probably manually quit competitors on WCA Live for the relevant rounds?

Additional context
We are planning to use this new regulation at Singapore Championship 2025 on 7-9 Feb 2025, thanks.

[dunkOnIT]

Thanks for raising this! We will work to have it implemented by Singapore Championships - please feel free to comment on this issue again in ~1 month for a progress update