Add shortcut RelativePath regression tests

[valar12]

Motivation

• Lock down the OneDrive shortcut behaviors that were exercised while fixing subfolder shortcut creation/removal.
• Prevent regressions around root creation, RelativePath placement, RelativePath removal, idempotent reruns, and conflict handling.

Description

• Added Set-odscexShortcutState regression coverage for:
  • creating a shortcut at the OneDrive root
  • creating a shortcut directly in a RelativePath folder
  • treating an existing matching RelativePath shortcut as compliant
  • ConflictAction Skip, Error, Replace, and Rename inside RelativePath
• Added a new Remove-odscex test file covering removal from a RelativePath folder.

Testing

• pwsh -NoLogo -NoProfile -Command '$PesterConfiguration = New-PesterConfiguration; $PesterConfiguration.Run.Path = "tests"; $PesterConfiguration.Run.Exit = $true; $PesterConfiguration.Output.Verbosity = "Detailed"; Invoke-Pester -Configuration $PesterConfiguration' - 20 passed
• git diff --check