Added basic set tests to `HelloWorld.hs`

[B-rando1]

This ensures that sets are being tested.

It also shows that sets are not implemented properly in Julia, as HelloWorld.jl crashes when run. I will create a separate issue for this.

[B-rando1]

P.S. once #3939 is merged, we should add lines checking setAdd and setRemove.

[JacquesCarette]

So, I shouldn't merge this until that's done?

[B-rando1]

I'd say it's up to you. These changes are fine as-is. I'd just want to add a line for each of the new functions added in #3939, with assert statements checking that they work correctly.

Since #3939 is waiting on union in C++, it might be good to merge this and make the further changes after it gets merged. Or you could add the changes directly to #3939. That might be better, since currently that PR has no code actually testing the functionality being added.