IFileInfo.PhysicalPath is empty

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Describe the bug

I have a web application where I can upload files. The files are associated with data in a database. In the database I only store the relative file path to the uploaded file. The file as such should be stored in a special folder in my wwwroot like `wwwroot/uploads/<>/` where <> will be the Id of the entity in the database.

With the following code I try to create the file:

```csharp
private IWebHostEnvironment _env; // will be set in the constructor

private void StoreFile(string path, string content)
{
var fi = new FileInfo(_env.WebRootFileProvider.GetFileInfo(path).PhysicalPath);
if (!fi.Directory.Exists)
fi.Directory.Create();

using (var writer = fi.CreateText())
{
writer.Write(vm.Content);
}
}
```

So when I try to run this code, I discovered, that the `PhysicalPath` of the `IFileInfo` is null because the file doesn't exist.


But I already did something like that in an earlier project (.Net < 6.0) and with that it worked fine. The `PhysicalPath` wasn't null, even when the file doesn't exists.

After some debugging I found out, that the `WebRootFileProvider` of the `IWebHostEnvironment` is a `Microsoft.Extensions.FileProviders.CompositeFileProvider` which contains two extra file providers:

1. Microsoft.AspNetCore.StaticWebAssets.ManifestStaticWebAssetFileProvider and
2. Microsoft.Extensions.FileProviders.PhysicalFileProvider


In the debug console of VSCode I did some test and I found that if I call the PhysicalFileProvider directly, the IFileInfo conains the physical path even if the file doesn't exists:


The implementation of the `IFileInfo` is of type `PhysicalFileInfo`

But when I use the `ManifestStaticWebAssetFileProvider` I get the the result with the null value:


The implementation of the `IFileInfo` is now of type `NotFoundFileInfo`.

### Expected Behavior

The physical path should be set nonetheless if the file exists or not.

### Steps To Reproduce

Try to create a new file with the code above.

### Exceptions (if any)

_No response_

### .NET Version

6.0.125

### Anything else?

```
.NET SDK (reflecting any global.json):
Version: 6.0.125
Commit: e898a826c2

Runtime Environment:
OS Name: ubuntu
OS Version: 22.04
OS Platform: Linux
RID: ubuntu.22.04-x64
Base Path: /usr/lib/dotnet/sdk/6.0.125/

global.json file:
Not found

Host:
Version: 6.0.25
Architecture: x64
Commit: 492abbeef0

.NET SDKs installed:
6.0.125 [/usr/lib/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.25 [/usr/lib/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.25 [/usr/lib/dotnet/shared/Microsoft.NETCore.App]
```

The application runs in a Codespace-Container.