Correct Erroring Default Variable Assignments on Systems with unique file paths

[buidav]

🗣 Description

• Make DefaultOutPath work on UNC file systems.
• Add a try catch to the DefaultOPAPath assignment.

💭 Motivation and context

Closes #1315
Closes #1369

🧪 Testing

• Try to run Import-Module .\PowerShell\ScubaGear on a non-Windows system.
• Try to run Import-Module .\PowerShell\ScubaGear on system using UNC file paths.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• PR targets the correct parent branch (e.g., main or release-name) for merge.
• Changes are limited to a single related goals ;) - eschew scope creep!
• Changes are sized such that they do not touch excessive number of files.
• These code changes follow the ScubaGear content style guide.
• Related issues these changes resolve are linked preferably via closing keywords.
• All relevant type-of-change labels added.
• All relevant project fields are set.
• All relevant repo and/or project documentation updated to reflect these changes.
• All relevant functional tests passed.
• All automated checks (e.g., linting, static analysis, unit/smoke tests) passed.

✅ Pre-merge checklist

• PR passed smoke test check.

• Feature branch has been rebased against changes from parent branch, as needed

  Use Rebase branch button below or use this reference to rebase from the command line.

• Resolved all merge conflicts on branch

• Notified merge coordinator that PR is ready for merge via comment mention

✅ Post-merge checklist

• Feature branch deleted after merge to clean up repository.
• Verified that all checks pass on parent branch (e.g., main or release-name) after merge.

[adhilto]

Code changes look good. Tested on a Windows, changes don't break default behavior (as expected). Deferring to @amart241 to test on a Mac.

[rmoffitt-m]

I tested this successfully on a Mac. Worked after manually installing the executable.

[rmoffitt-m]

Successful test when manually downloading opa. Didn't use Install-OPAforSCuBA which seems to use a different filename (opa_darwin_amd64) but that's likely a separate issue.

[buidav]

@nanda-katikaneni this is ready to merge
Smoke tests pass: https://github.com/cisagov/ScubaGear/actions/runs/12241996054/job/34149015595

[tkol2022]

I tested on a windows system using UNC paths. No errors.