AggregateException happens if exception occurs before AddRazorRuntimeCompilation()

A change appears to have been made between .NET Core 3.1 and 5.0 which causes an `AggregateException` to happen if, in an ASP.NET Core web app, an exception occurs before `.AddRazorRuntimeCompilation()` occurs.

I wrap my `ConfigureServices` code in a try/catch block so that if an exception occurs, I can catch it and put out a friendly, basic, HTML error message. In .NET Core 3.1, this would break into my `catch` block, and my code would be able to output a basic message with the "Hello world" exception message:

```
throw new Exception("Hello world");
services
.AddControllersWithViews(opt => {
opt.Filters.Add(new AutoValidateAntiforgeryTokenAttribute());
})
.AddRazorRuntimeCompilation();
```

In 5.0, my catch block never runs, and I get an immediate `AggregateException`:

```
Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Mvc.Razor.Compilation.IViewCompilerProvider Lifetime: Singleton ImplementationType: Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.RuntimeViewCompilerProvider': Unable to resolve service for type 'Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartManager' while attempting to activate 'Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.RuntimeViewCompilerProvider'.) (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.RazorReferenceManager Lifetime: Singleton ImplementationType: Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.RazorReferenceManager': Unable to resolve service for type 'Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartManager' while attempting to activate 'Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.RazorReferenceManager'.) (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.CSharpCompiler Lifetime: Singleton ImplementationType: Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.CSharpCompiler': Unable to resolve service for type 'Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartManager' while attempting to activate 'Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.RazorReferenceManager'.)
```

This is a rather unfortunate change as it means the only safe way for me to use the Razor runtime compilation is to put the call right at the top of my `ConfigureServices`. I assume something weird is going on at build time, too, because if I remove the call to `.AddRazorRuntimeCompilation()`, the exception is once again caught in my `catch` block.

I think the behaviour should be reverted to how it was in .NET Core 3.1.