Performance logging and counters:

* Tally and duration counters for Job Queue tasks and RPC calls
    optionally rendered by server_info and server_state, and
    optionally printed to a distinct log file.
    - Tally each Job Queue task as it is queued, starts, and
      finishes running. Track total duration queued and running.
    - Tally each RPC call as it starts and either finishes
      successfully or throws an exception. Track total running
      duration for each.
  * Track currently executing Job Queue tasks and RPC methods
    along with durations.
  * Json-formatted performance log file written by a dedicated
    thread, for above-described data.
  * New optional parameter, "counters", for server_info and
    server_state. If set, render Job Queue and RPC call counters
    as well as currently executing tasks.
  * New configuration section, "[perf]", to optionally control
    performance logging to a file.
  * Support optional sub-second periods when rendering human-readable
    time points.

src/test/consensus/ScaleFreeSim_test.cpp

@@ -57,7 +57,7 @@ class ScaleFreeSim_test : public beast::unit_test::suite
 
         // nodes with a trust line in either direction are network-connected
         network.connectFromTrust(
-            round<milliseconds>(0.2 * parms.ledgerGRANULARITY));
+            date::round<milliseconds>(0.2 * parms.ledgerGRANULARITY));
 
         // Initialize collectors to track statistics to report
         TxCollector txCollector;