test(rules): rstest framework

[supermaxiste]

Proposed Changes

Replaced previous rule tests with new tests following the rstest framework. Now we have 1 test function per rule, with each function testing different scenarios.
Example of previous code structure:

#[test]
    fn rule1_example1() {
    mask = rule1(example1)
    assert!(mask.is_set())
}
#[test]
    fn rule1_example2() {
    mask = rule1(example2)
    assert!(mask.is_set())
}

Example of ✨ new ✨ code structure:

#[rstest]
#[case(example1)]
#[case(example2)]
   fn rule1(case)  {
   mask = rule1(case)
   assert!(mask.is_set())
}

Addresses #25

Types of Changes

• A bug fix (non-breaking change which fixes an issue).
• A new feature (non-breaking change which adds functionality).
• A breaking change (fix or feature that would cause existing
  functionality to not work as expected).
• A non-productive update (documentation, tooling, etc. if none of the
  other choices apply).

Checklist

• I have read the
  CONTRIBUTING
  guidelines.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added the necessary documentation (if appropriate).

[cmdoret]

This is much better and a perfect fit for this use-case!

I proposed to remove constant arguments with the objective of improving readability. Let me know if you think this is not a good idea.

[supermaxiste]

Thank you @cmdoret and very good suggestion!

For 2 out of 3 rules I left a simple assert and removed the argument that were constant across cases 👍
For the type_rule we do test both subjects and objects being either masked or not, so I left the cases as they are.

[cmdoret]

🙌