Update unused function parameters with wildcard variables

[mitchelbaker-cisa]

🗣 Description

Rego compilation errors were being thrown due to unused function parameters. For each instance parameters were changed to the wildcard variable "_".

💭 Motivation and context

Resolves issue #195, OPA versions 0.50+ introduce updates to strict mode checking for unused variables. For newer versions of OPA, ScubaGear's automated checks will fail preventing merges into main from happening.

Although this PR addresses the strict mode errors in Rego policies, it does not address the OPA executable version downloaded in OPA.ps1 or the version specified in Run OPA tests workflow, #593.

🧪 Testing

To test these changes:

1. Go to OPA documentation, select the version you want to test, then download the executable
2. Run the OPA strict mode check

.\opa_windows_amd64.exe check Rego Testing\Unit\Rego --strict

3. Repeat steps for other versions and rerun the strict mode check as needed

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Rebase feature branch against parent branch and make sure tests still pass
• Add comment ready for merge and mention the merge coordinator

[Sloane4]

All unit test pass & run successfully on G5

[schrolla]

Tested the branch using the updated 0.58.0 OPA engine in strict mode and passed.
Ran Invoke-Scuba -p * using updated branch and OPA 0.58.0 with no issues and compared results to same invocation on main branch using OPA 0.42.1. Results were identical.
All unit tests passed using OPA 0.58.0.
Everything looks good here.

[schrolla]

@mitchelbaker-cisa Since OPA 0.59.0 just dropped. I would recommend running a quick test against it as well before rebasing the branch so it's ready for merge.