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).

out フォルダーから PSScriptAnalyzer フォルダーをコピーするテスト設定と、Tests/Engine/LibraryUsage.tests.ps1 の 214 行目で発生する失敗から始めます。Windows PowerShell での失敗を再現し、その後、テストの実行で $env:PSModulePath の先頭にある out フォルダーが使用され、モジュールをコピーしなくてもテストスイートがパスすることを確認します。