`RazorFileSystem.GetItem("/").PhysicalPath` obsolete side effects

Historically, I've been able to get my project root directory from Razor by using the following line:

```c#
RazorProjectFileSystem razorFileSystem = webApp.Services.GetRequiredService();
Console.WriteLine(razorFileSystem.GetItem("/").PhysicalPath) // c:\path\to\project\root
```

But, I see that `RazorProjectFileSystem` is being obsoleted along with Razor runtime compilation.

Is there another way to get the project root directory from Razor? I currently have a Razor page manager class in which it does everything it needs to do without me having to manually give it my project's root directory. Without `razorFileSystem.GetItem("/").PhysicalPath`, I will have to add another argument to my page manager class's constructor.