[Feature Request] add tower::Service implementation for http::Request and http:: Response types.

[alekseysidorov]

reqwest::Client already has tower::Service implementation for the reqwest::Request and reqwest::Response types. But it lacks of the service implementation for http::Request and http::Response types. If we add this implementation we can use a lot of existing layers from the tower_http crate without any code modification.

I already implemented this feature in my own crate. But I believe it would be better to add this functionality to the core library than to use adapters.

Here is my implementation.