In this PR, we make the appropriate backend service changes in order to enable the login migrations feature in the SQL migration extension.
Changes include:
updating the Microsoft.SqlServer.Migration.Login NuGet version to the latest version
adding a new request handler for StartLoginMigrations calls, which makes the appropriate calls to the login NuGet
adding ExtensionMethod helper to properly combine exception maps login migration nuget calls
Co-authored-by: Akshay Mata <akma@microsoft.com>
