feat(rego): add result package

[nikpivkin]

The purpose of this change is to improve testing of REGO policies by removing the dependency on trivy-iac and adding a new result package to the library.

Currently, it is not possible to test REGO policies because the result.new function that is used in all policies is declared in trivy-iac using the OPA sdk. This PR adds a new result package to the library, thus removing the dependency on trivy-iac.

Two functions have been moved:

• is_managed - checks that the metadata is managed
• new - returns structured result, which is needed for further analysis by the REGO policy scanner.

The new function signature remains the same, which ensures backward compatibility. The isManaged function has been renamed to is_managed.

[nikpivkin]

This change will cause a backwards compatibility break for users who do not upgrade Trivy to a version that contains this change. Therefore, this PR will be in draft until a solution for this problem is found.