Mark entrances as "possible" when having the right item

[hellow554]

When doing an entrance randomizer, entrance that have no partner are marked as a black door with a red exclamation mark. But sometimes you can't get to the other side because an item (hookshot, boots, Flippers, ...) is missing.

I would like to distinguish the situation where you can't reach the other end vs you haven't reached the other end yet.

Should be feasible, right?

[kbranch]

When I had thought about this in the past, I decided that it would require analyzing the logic graph more than I currently do. Definitely possible, but not trivial.

Thinking about it again, though, I think I can use the existing metadata to cheat it a bit and do it relatively simply. No promises on when, but I'll move this up the priority list.