Add support for intra-cluster tracing

[codefromthecrypt]

Currently, the Cassandra implementation does not implement outbound tracing. This means a trace won't include spans that cross nodes within the cluster.

[michaelsembwever]

i'm working on this…

in the meantime one can still use https://github.com/thelastpickle/cassandra-zipkin-tracing

[nisc-acooper]

This is a pretty stale issue, but wanted to ping on it quick. Was this effort abandoned? We are currently working on zipkin support in our clusters and realized a gap between these two projects (last pickle vs brave-cassandra). LP supports cross-server tracing, but brave-cassandra supports B3 protocol.

[codefromthecrypt]

At some point there was a problem in cross-cluster propagation, but it probably fixed itself by now (don't recall the datastax driver variant).

At any rate, testing this will have to be done with care to see how large the trace graphs become. That should be proven out with unit tests. this is a volunteer based project, so what happens is if someone wants to work on something they contribute help. I'll set this to help-wanted and if you are interested, I'd bet someone would help review.