[Routing] Move to GenericHost

[Kahbazi]

Part of #20964

[javiercn]

Thanks for the contribution!

Waiting for the tests to pass to merge

[Tratcher]

I found a few more:

aspnetcore/src/Http/Routing/test/FunctionalTests/EndpointRoutingSampleTest.cs

Line 21 in 527096a

var webHostBuilder = Program.GetWebHostBuilder(new[] { Program.EndpointRoutingScenario, });

aspnetcore/src/Http/Routing/test/testassets/RoutingWebSite/Program.cs

Line 60 in 527096a

return new WebHostBuilder()

aspnetcore/src/Http/Routing/test/testassets/RoutingSandbox/Program.cs

Line 60 in 527096a

return new WebHostBuilder()

aspnetcore/src/Http/Routing/test/testassets/Benchmarks/Program.cs

Line 17 in 527096a

public static IWebHostBuilder GetWebHostBuilder(string[] args)

aspnetcore/src/Http/Routing/test/FunctionalTests/Benchmarks/EndpointRoutingBenchmarkTest.cs

Line 22 in 527096a

var webHostBuilder = Benchmarks.Program.GetWebHostBuilder(args);

aspnetcore/src/Http/Routing/test/FunctionalTests/WebHostBuilderExtensionsTest.cs

Line 82 in 527096a

var webhostbuilder = new WebHostBuilder();

[Tratcher]

There's an unrelated CI build break. We'll look into it.

[JamesNK]

Looks good. Test failure seems unrelated. I've triggered a rerun.

[davidfowl]

Why aren't we using auto merge on these?

[BrennanConroy]

Thanks for all these @Kahbazi !