Add alternate unlock condition for Burial Grounds

[josephcsible]

There are several geometries (e.g., arbitrary tilings loaded from .tes files) that will result in Burial Grounds being in-game, but Kraken Depths not. This makes it impossible to ever unlock Burial Grounds, and thus also impossible to complete the Hyperstone Quest. It should have some alternate unlock condition, like how Blizzard does when Windy Plains isn't in-game.