This is a cluster-layout.zeek template that can be copied into a testing
directory if needed. The idea is that a developer sets environment
variables within their btest and the Cluster::nodes variable is
implicitly extended by appropriate nodes.
For example, using @TEST-PORT BROKER_LOGGER1_PORT will add an appropriate
logger-1 node to Cluster::nodes, based on the existence of the
BROKER_LOGGER1_PORT environment variable.
(cherry picked from commit a56744a2679c3bd42b4046f2687ccc8fb8442485)
