Adding decorator moves OnActivated event invocation

Given the following service/container setup:

```cs
public class OuterService
{
public OuterService(IMiddleService middle) => Console.WriteLine("Outer");
}

public interface IMiddleService {}

public class MiddleService : IMiddleService
{
public MiddleService(InnerService inner) => Console.WriteLine("Middle");
}

public class InnerService
{
public InnerService() => Console.WriteLine("Inner");
}

builder.RegisterType().SingleInstance();
builder.RegisterType().SingleInstance().As();
builder
.RegisterType()
.SingleInstance()
.OnActivated(_ => Console.WriteLine("Inner activated"))
;
```

I observe the following output on resolving `OuterService`:

```
Inner
Middle
Outer
Inner activated
```

Note that activation event fires _last_ (which allows us, for example, resolve circular dependency, were `Inner` to depend on `Outer`).

Now we add a decorator (everything else stays the same):

```cs
public class Decorator : IMiddleService
{
public Decorator(IMiddleService inner) => Console.WriteLine("Decorator");
}

builder.RegisterDecorator();
```

The output is:

```
Inner
Middle
Decorator
Inner activated
Outer
```

Now the activation event fires after _decorator_, not the last in the pipeline (which in our case brings back circular dependency).

Observed on Autofac 6.2 and 6.5.

Start by reproducing the issue with RegisterType, OnActivated, and RegisterDecorator using the setup in the report. Trace the activation and decorator pipeline to compare both registration paths. Done means the OnActivated callback runs after the complete decorated service pipeline, including the decorator, without changing the non-decorated behavior.

Written by the indexing model from the issue text.