Remove support for chained IServiceProvider fallback from ServiceProvider

- Replaced with explicit IServiceManifest/IServiceCollection.Import
- Still need to verify all up: hosting/routing/mvc/identity repo changes

cc @davidfowl @lodejard @halter73 @divega 

Please review the tests and container code removed carefully, they all appeared to be testing/related to fallback, but I'm not 100% sure
You can build a ServiceProvider out of any `IEnumerable<IServiceDescription>` is the idea I think, `IServiceCollection` is an `IEnumerable<IService`, so normally this doesn't cause any issues