Stardew valley: Add Trap Distribution setting

[agilbert1412]

What is this fixing or adding?

I originally wanted to put this in 7.x.x, but I figured out a decent way to make this work without being a breaking change in the mod. So in the spirit of making smaller, more incremental PRs, I decided to submit it as is.

This adds an option that allows users to specify a distribution for traps (assuming they enabled traps at all). They can use it to disable certain traps, or change how many they'll get of each.

As OptionDict() doesn't work on webhost, this is a yaml-only setting. If it ever gets added to webhost, I added it to groups properly and it'll work day1.

This only impacts the chances of rolling each trap. In practice, there will still be variation.

Lastly, to make this work, I had to do a refactor. Our class items.py has been split into two item_classes.py and item_creation.py. This is to break up a circular dependency, where item_creation needs options, but now the options need the item_classes to build the Schema for this option.

How was this tested?

Added some tests specifically for this, but since the feature is inherently random, the test cannot have 100% success rate. It is always possible that a freak seed ends up generating many of a trap that was requested with low odds, for example.
So I locked these tests behind one of our flags that makes it not run in the github pipeline, only with our specific local run configs. This way, the rare failure won't bother anyone except us.

I also generated a couple seeds with various odds to see the number of resulting traps matching the expected ballparks.

[Jouramie]

I think the comments on the weights parameter really need to be addressed, as this probably hit the performances a lot because of the loop. The potential caching issue in the tests needs to be validated as well. The rest is pretty minor.

[Jouramie]

Just nitpicking, LGTM