Remove DoH Retry for NXDOMAIN

[adhilto]

🗣 Description

• Adjust DNS query logic so that a retry over DoH is not triggered by NXDOMAIN.
• Make EXO PowerShell compliant with the new linter

💭 Motivation and context

Closes #764. Aims to reduce warning fatigue.

🧪 Testing

• Ran against the regular testing tenant, all results are correct
• Ran the Invoke-RobustDnsTxt function in one of the pilot environments that has the empty DNS response issue. Retries over DoH still occurred as designed.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• 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.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

[crutchfield]

Looks good. Linter errors not related to PR.

[nanda-katikaneni]

Looks good - done a few tests with existing test tenants, no issues. Approving.