When multiple loggers are configured in a Supervisor controlled cluster
configuration, encode extra information into the rotated filename to
identify which logger produced the log.
This is similar to the approach taken for ZeekControl, re-using the
log_suffix terminology, but as there's only a single zeek-archiver
process and no postprocessors and no other side-channel for additional
information, we encode extra metadata into the filename. zeek-archiver
is extended to recognize the special metadata part of the filename.
This also solves the issue that multiple loggers in a supervisor setup
overwrite each others log files within a single log-queue directory.
