[Tracing] Add more span attributes

[ktoso]

We could further refine how many span attributes we set, currently only the bare minimum of request method is set.

[czechboy0]

As I'm starting to use this in practice, I agree we need to add more. Some for consideration, based on what a well-instrumented server reports (we should mirror the similar attributes on the client side):

• http.request.body.size
• http.response.body.size
• http.response.status_code (right now we set the legacy http.status_code)
• network.peer.address
• network.peer.port
• network.protocol.version
• url.path
• url.scheme
• server.hostname
• server.port