Add ability to shuffle molehills anywhere

The new custom collectible already allows for this, but Cal has said logic may not be ready to handle them being anywhere but not sure what's needed to make it work. Ideally we'd provide a dropdown to shuffle off, between molehills, or anywhere.

Start by locating the custom collectible shuffle logic and the existing shuffle-choice UI. Read how the current off and between-molehills options are represented, then determine what is needed for an anywhere option. Done means the dropdown exposes all three choices and molehills can be shuffled anywhere without breaking the existing choices.

Written by the indexing model from the issue text.