endStage event is processed after a new turn starts

[delucis]

If a move that calls events.endStage() triggers the end of the turn (via an endIf for example), then that endStage event is currently run after the set-up for the new turn. This can result in the player who moved last being removed from the activePlayers for the new turn.

Reported on Gitter by @tomnunn who shared this CodeSandbox reproduction.

(This is effectively a duplicate of #769, which reports the inverse problem that an endIf doesn’t yet have access to the new activePlayers.)