Add coop features

[cjmang]

What feature would you like to see?

There are cases where it's nice to be able to handoff the same world between different people, such as in asyncs where games get dropped. With RPGs like GS, local progressive items would need to be reobtained from their source location, which can be a bit of a pain.

Emerald has a feature where you can make various categories of items be obtained via the client, even if the item is placed locally. A similar feature would be very helpful here in GS. Would require client changes and generation changes.

[Dragion147]

As inspiration, here are the settings as defined in the yaml for Pokemon Emerald regarding remote items

 remote_items:
   # Instead of placing your own items directly into the ROM, all items are received from the server, including items you find for yourself.
   # 
   # This enables co-op of a single slot and recovering more items after a lost save file (if you're so unlucky).
   # 
   # But it changes pickup behavior slightly and requires connection to the server to receive any items.
   'false': 50
   'true': 0