Enforce powershell linter rules

[mitchelbaker-cisa]

🗣 Description

The linter workflow was configured to always pass despite any relevant warnings found. There have been situations where code that did not meet the linter's standards were merged into main. The placement of continue-on-error has been updated so the workflow catches relevant errors.

All PowerShell warnings have been addressed except for two files which call Invoke-Expression. The change is trivial but requires additional testing of SetupTestbed.ps1/install_lme.ps1 which is out of scope for this PR. See the issue below for more info.

💭 Motivation and context

Improves our CI/CD integrations and overall testing of LME.

Resolves #175

Additional todos after this PR is merged:

• [BUG] Address the use of Invoke-Expression  #327
• [BUG] Address linting errors from main.yml workflow #328

🧪 Testing

Ran the main.yml Github action, checked warnings/errors from PSScriptAnalyzer and applied necessary changes.

✅ Pre-approval checklist

• Changes are limited to a single goal AND
  the title reflects this in a clear human readable format
• Issue that this PR solves has been selected in the Development section
• I have read and agree to LME's CONTRIBUTING.md document.
• The PR adheres to LME's requirements in RELEASES.md
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated to reflect the changes in this PR.

✅ Pre-merge Checklist

• All tests pass
• PR has been tested and the documentation for testing is above
• Squash and merge all commits into one PR level commit

✅ Post-merge Checklist

• Delete the branch to keep down number of branches