cluster/supervisor: Multi-logger awareness

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.

NEWS

@@ -116,6 +116,10 @@ New Functionality
   ``make-archive-name`` script and using the new ``ZEEK_ARG_LOG_SUFFIX``
   environment variable.
 
+- A supervisor controlled Zeek cluster is now multi-logger aware. This avoids
+  loggers overwriting each others log files within a single log-queue directory.
+  By default, a logger's name is appended to the rotated logs by zeek-archiver.
+
 - Introduce a new command-line option ``-V`` / ``--build-info``. It produces
   verbose output in JSON format about the repository state and any included
   plugins.