Assert invariants

[saik0]

Invariants we could assert:

• Array store is sorted
• Array store is deduplicated
• Bitmap store length is correct
• Roaring containers are sorted by key
• Roaring datastructure len is correct in Constant time len #182

I think debug asserting this for every mutation and creation would be best.

[reneleonhardt]

@Kerollmops Any news on testing invariants?

[Kerollmops]

Hey @reneleonhardt 👋

Thank you for your interest in this project. I haven't got much time to work on this. However, I think that's not something very hard to work on, so I labeled it good first issue.

Feel free if you want to spend time on that. Running the fuzzer for a long time will be enough to validate that no invariant is broken.

Have a nice day 🏜️