Call id propagation

[iansmith]

Currently, we are not passing the call id to every place that it needs to go. A call id should be generated the initial call site (in a client) and then pushed (via the pctx) to all downstream calls. This data needs to also be added to the LogRequest so that all log messages have the call id on them.

Further, the log viewer application should probably do bookkeeping to keep all the calls in a particular chain (sharing the same call id) are grouped together.