Update the Worker template to use the `Host.CreateApplicationBuilder` API.

[IEvangelist]

Update the Worker template to use the Host.CreateApplicationBuilder API.

[eerhardt]

We should reconsider updating the Worker template to Host.CreateApplicationBuilder in .NET 8. The callback approach that Host.CreateDefaultBuilder uses is no longer recommended going forward, and the programming model is no longer used in ASP.NET apps - it uses the WebApplication.CreateBuilder() API which is imperative, top-to-bottom programming. The Worker template should follow the same pattern.