Add a better error message for the incompatibility between Scarce/Minimal and high heart win conditions

[fenhl]

Fixes #1644. The fix chosen here is to add an explicit check for the incompatible settings to the world constructor and inform the user how to fix it. My opinion is that allowing the user to choose which fix to apply (changing item pool vs changing wincons) is better than silently changing the number of hearts in the item pool, which the user may not expect, especially if we end up separating the heart pool from the remaining item pool, which is a common suggestion and probably a good idea. Besides, even if we want to change the behavior later, this is an easy fix that should be included until then.

[cjohnson57]

I'm not sure I agree with this. If the user wants to use heart conditions on a scarcer item pool, they should be able to do so.

You could argue that it's fair to require them to use a plando for this, but the code doesn't seem to check the item pool itself (which plando would affect), just assuming how many hearts will be available based on the item pool setting.