Include moat circumvention countries in the build (tor-browser part)

Spun out from #42605 (comment 3056965).

In discussions, I think we basically concluded that we can include the list of circumvention countries at build time instead of fetching them from Moat.

In principle, we could update the list once during the first auto bootstrap, when we already call Moat with consent. But I'm not sure how necessary or useful this would be.

@pierov do you have a preference for how to implement this in tor-browser-build? Would you want to have a separate file, like we did with pt_config.json, or just a user preference?