Being able to run tests by setting $PsModulePath instead of XCopy to one of those folders

As discussed internally. Instead of doing a Copy-Item of the PSScriptAnalyer folder in the out folder to the first $env:PSModulePath folder (where it can override an existing installation due to the version number being the same), we should just be able to just set add the out folder to the beginning of the $env:PSModulePath variables during test execution. However, this does not even work for Windows PowerShell at the moment due to the LibraryUsageTests (I get one failure here).

從複製 out 資料夾中的 PSScriptAnalyzer 資料夾的測試設定，以及 Tests/Engine/LibraryUsage.tests.ps1 第 214 行的失敗開始。重現 Windows PowerShell 的失敗，然後驗證測試執行使用位於 $env:PSModulePath 開頭的 out 資料夾，並且無需複製模組測試套件即可通過。