Consider proptest and libfuzzer for testing contracts

I think it would benefit on fuzztest and property test of contracts.

The fuzztests addresses the issue, that when contract crashes, the error message turns out not being nice. Detecting potential crashes early and having example how to integrate those to new contracts, so it would be easier to handle this kind of ptoblems.

Proptest is just a way to slightly generalize tests to easier find bugs in edge cases,