RequestLocalizationMiddleware does not handle CultureInfo.InvariantCulture since version 8

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug

The RequestLocalizationMiddleware sets the culture to default even if the ```RequestLocalizationOptions``` supports ```CultureInfo.InvariantCulture``` since version 8.

Example:
```c#
builder.Services.Configure(options => {
var supportedCultures = new[]
{
CultureInfo.InvariantCulture,
CultureInfo.GetCultureInfo("fr"),
CultureInfo.GetCultureInfo("en"),
};

options.DefaultRequestCulture = new(supportedCultures[1]);
options.SupportedCultures = supportedCultures;
options.SupportedUICultures = supportedCultures;

options.RequestCultureProviders =
[
new DefaultRequestCultureProvider()
];
});

public class DefaultRequestCultureProvider : IRequestCultureProvider
{
public Task DetermineProviderCultureResult(HttpContext httpContext)
{
var result = new ProviderCultureResult(culture: CultureInfo.InvariantCulture.Name, uiCulture: CultureInfo.CurrentUICulture.Name);

return Task.FromResult(result);
}
}
```

At the end, ```CultureInfo.CurrentCulture``` was always the ```DefaultRequestCulture``` instead of ```CultureInfo.InvariantCulture```.

Note: this code worked until version 8

### Expected Behavior

_No response_

### Steps To Reproduce

_No response_

### Exceptions (if any)

_No response_

### .NET Version

_No response_

### Anything else?

_No response_