fix: reference utils files relative to policy lib directory

[jpts]

Description

The location of utils rego files are currently hardcoded. If we move the lib folder to outside the current directory, the utils rego files cannot be found.

Motivation and Context

This PR locates the utils rego files relative to the lib path specified on the CLI.

How Has This Been Tested?

I have built the binary with changes and tested locally.

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes if appropriate.
• [ ] All new and existing tests passed.

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