Remove dependency on DependencyInjection and instead use DependencyInjection.Interfaces on Http.Extensions

[davidfowl]

https://github.com/aspnet/HttpAbstractions/blob/dev/src/Microsoft.AspNet.Http.Extensions/project.json#L7

[davidfowl]

/cc @Praburaj

[Praburaj]

@davidfowl Http.Extensions seems to have dependency over DependencyInjection as it requires ActivatorUtilities to instantiate the middleware object in the UseMiddleware extension. Not sure if there is an alternate for this.

[Praburaj]

Merged 93deb0b