Update ASP.NET Core C# project templates to use new minimal hosting APIs in .NET 6

[DamianEdwards]

The ASP.NET Core project templates included in the SDK should be updated to use the new minimal hosting APIs introduced in .NET 6 as they represent the new idiomatic way to bootstrap (configure and start) the relevant host for the majority of scenarios.

• The CreateHostBuilder method would be removed as the patterns that were previously reliant on this are no longer necessary
• The Startup class would be removed and its contents applied as applicable to the calls to WebApplicationBuilder in Program.cs
• Change to Blazor WebAssembly hosted templates tracked in Update blazorwasm-hosted templates to use minimal host #32471

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We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
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[Tratcher]

FYI @jmprieur @jennyf19

[jmprieur]

@DamianEdwards : are there examples of the new projects (or already converted templates?)?
cc: @Tratcher @jennyf19

[Tratcher]

@jmprieur see https://github.com/dotnet/aspnetcore/blob/b9efadc59ddbf6743775244622fb95301dd1846c/src/ProjectTemplates/Web.ProjectTemplates/content/EmptyWeb-CSharp/Program.cs

[jmprieur]

Thanks @Tratcher. I didn't even know that this could build.
Where would you do the services.AddAuthentication() ? and the app.UseAuthentication() ?

[Tratcher]

Services are on builder.Services, app.UseAuthentication() goes between the exception handlers and the routes.

We'll update the StarterWeb templates and then you can copy or iterate on those as needed.