Record the node, reply size, and time of each call

Each line of usage.jsonl also gives the length of the call in seconds,
the size of the text of the reply in bytes, and, for a compaction, the
node [l, i] that it builds. With these fields the records show the size
of each try of a node, the time per call, and how many calls ran at
once, also when eight builds run in parallel and the order of the calls
no longer tells which node a call belongs to.

The compactor names the node on its requests. The node goes only to the
usage file and never to the endpoint.

Issue: b14d537