Instrument tracing spans for RPC data columns requests and responeses

[jimmygchen]

Instrument the RPC request and response handling code paths using tracing spans to enable end-to-end visibility of data column rpc interactions with peers, e.g. what rpc requests each client are sending, and their success rate of serving requests.

Questions to answer

• what columns are clients requesting? are any extra non-advertise columns requested?
• what columns are clients responding with? are there any missing columns
• what is the duration and success rate for RPC responses

fields to include

• peer_id
• client

Root spans

active_custody_request

Traces the entire duration of a custody request, which contains one to many batch_columns_req spans, each mapped to an actual RPC request with a peer_id.

[jimmygchen]

Data column RPC paths instrumented in #7831