AddUsingDirectiveIfNeeded is whitespace-sensitive

## File a bug

### Include your code

```C#
using Microsoft .Extensions .DependencyInjection;
```

### Include stack traces

```
System.AggregateException: One or more errors occurred. (There was an error creating a DbContext :/home/dell/prog/Scaffolding/tools/dotnet-aspnet-codegenerator/Startup.cs(7,7): warning CS0105: Dyrektywa using dla elementu „Microsoft.Extensions.DependencyInjection” już wystąpiła w tej przestrzeni nazw
at Microsoft.VisualStudio.Web.CodeGeneration.EntityFrameworkCore.EntityFrameworkModelProcessor.Process() in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG.EFCore/EntityFrameworkModelProcessor.cs:line 226
at Microsoft.VisualStudio.Web.CodeGeneration.EntityFrameworkCore.EntityFrameworkServices.GetModelMetadata(String dbContextFullTypeName, ModelType modelTypeSymbol, String areaName, Boolean useSqlite) in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG.EFCore/EntityFrameworkServices.cs:line 138
at Microsoft.VisualStudio.Web.CodeGenerators.Mvc.ModelMetadataUtilities.ValidateModelAndGetEFMetadata(CommonCommandLineModel commandLineModel, IEntityFrameworkService entityFrameworkService, IModelTypesLocator modelTypesLocator, String areaName) in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG.Mvc/ModelMetadataUtilities.cs:line 52
at Microsoft.VisualStudio.Web.CodeGenerators.Mvc.Razor.EFModelBasedRazorPageScaffolder.GenerateCode(RazorPageGeneratorModel razorGeneratorModel) in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG.Mvc/RazorPage/EFModelBasedRazorPageScaffolder.cs:line 93
at Microsoft.VisualStudio.Web.CodeGenerators.Mvc.Razor.RazorPageGenerator.GenerateCode(RazorPageGeneratorModel razorPageGeneratorModel) in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG.Mvc/RazorPage/RazorPageGenerator.cs:line 82
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
at System.Threading.Tasks.Task.Wait()
at Microsoft.VisualStudio.Web.CodeGeneration.ActionInvoker.b__8_0() in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG.Core/ActionInvoker.cs:line 102
at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args) in /home/dell/.nuget/packages/microsoft.extensions.commandlineutils.sources/6.0.0-preview.3.21166.3/contentFiles/cs/netstandard1.0/CommandLine/CommandLineApplication.cs:line 374
at Microsoft.VisualStudio.Web.CodeGeneration.ActionInvoker.Execute() in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG.Core/ActionInvoker.cs:line 54
at Microsoft.VisualStudio.Web.CodeGeneration.CodeGenCommand.Execute() in /home/dell/prog/Scaffolding/src/Scaffolding/VS.Web.CG/CodeGenCommand.cs:line 93
```

### Include provider and version information

Microsoft.VisualStudio.Web.CodeGeneration.Design/Microsoft.DotNet.MSIdentity version:

1.0.0

Target framework: (e.g. .NET 5.0)

6.0.1

Operating system:

Linux x64 5.15.12-1-default

IDE: (e.g. Visual Studio 2019 16.3)

1.63.2