* Detect a ConfigureDefaultBuilder static method on Program.cs of the test site
and use it to initialize the IWebHostBuilder instance that we configure for testing.
* Make use of the new service configuration extensibility points in Hosting to override
services for testing.
* Get rid of MvcWebApplicationBuilder and move MVC specific methods into extension methods.
- Move the Mvc.Performance project from test/ to benchmarks/.
- Remove the Version attribute on PackageReference.
- Add a reference to two PackageLineup's.
- Add snippet to README explaining the additional requirement to run build.cmd /t:restore.
- Add a target to check that packages have been pinned.