Fix catacombs backdrop being shorter than needed & support all catacombs floor variants properly. OverrideRockAltEffects now allows specifying RoomTypes. Added SetStageMusic for setting music for all default RoomTypes at once.

New backdrop system, floor and wall are split and all properly randomized.

Fix RunWhenLoaded table.

Some helper functions for mod load order, so addon mods to mods based on StageAPI are easier to pull off.

Room testing!
croom <ID or Name> <RoomListName (optional, uses current floor if not given)>

CountLayoutEntities and DoesLayoutContainEntity > DoesLayoutContainEntities.

DoesEntityMatchParameters, DoesLayoutContainEntity, improved layout overriding.

fix dark room having shading.

XL stage support, PRE_SELECT_NEXT_STAGE callback.

undo PRE_ROOM_ENTITY_SPAWN usage