refactor: migrate REGO functions to Go

[nikpivkin]

The rules declared in trivy-policy should not depend on this repository, so the functions result.new and isManaged should be moved.
Due to REGO language limitations, the result.new function cannot be fully implemented in REGO. Therefore, the basic logic of this function will be ported from REGO to Go code, providing the necessary functionality.

Now result.new returns the following structure and does not modify the data in any way:

{
  "msg": "message",
  "metadata": {...}
}

Backward compatibility with the previous flat structure returned by the result.new function has been preserved.

Related PRs:

• feat(rego): add result package trivy-checks#62

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