This PR fixes a crash in tests when the test `Env is run at trace/debug log level.
This issue only affects tests, and only if logging at trace/debug level, so really only relevant during rippled development, and does not affect production servers.
Combine multiple related debug log data points into a single
message. Allows quick correlation of events that
previously were either not logged or, if logged, strewn
across multiple lines, making correlation difficult.
The Heartbeat Timer and consensus ledger accept processing
each have this capability.
Also guarantees that log entries will be written if the
node is a validator, regardless of log severity level.
Otherwise, the level of these messages is at INFO severity.
