Add peer.service attribute to all service spans

[rogercoll]

Feature Request

The peer.service attribute helps to relate traces between services. We are currently using it in some services spans, but it would be great to add it to all spans. The attribute is defined in the semantic conventions: https://github.com/open-telemetry/semantic-conventions/blob/main/docs/attributes-registry/peer.md?plain=1#L15

Describe the solution you'd like:

Add the peer.service attributes to all the spans that make a request to known services.

[jmacd]

open-telemetry/oteps#247 (see also)