Make the cut Woodcarver boss battle accessible

Replaces the Trapper/Trader boss battle with the cut Woodcarver boss battle. Does not alter the battle itself, so while it may be playable it is also still unfinished. Just intended as a simple way to make this neat secret boss accessible. Why replace the Trapper/Trader boss? Well, the Woodcarver comes right before them in the game's Opponent.Type enum, so I personally believe the Woodcarver was originally going to be the boss of the Snow Line before it was changed to the Trapper/Trader. That's ultimately just my opinion, though.