text: Title: Enforce calling of `Case.call` in Python tests
  Body: In Python tests generated by Schemathesis, it's crucial to call `case.call` to execute the test case properly. However, users sometimes forget to include this call, leading to potential confusion and incomplete tests.
  
  However, there could be use cases like just collecting the generated tests - we use it in our test suite for further inspection. Probably we need to collect existing use cases first to assess the impact.