Introduce a test to verify that latest StateVersion is applied to new contract deployments

[petersalomonsen]

In order to prevent the scenario described in #69 to happen again, we should introduce a test to verify that the new method of lib.rs initialize the contract with the latest StateVersion.

Without such a test it is very likely that developers will break the migration test again because of forgetting to update the StateVersion also for new contract deployments.

The consequence of breaking the migration test is first of all that it's blocking PRs that follows.