client-cmds/nlean: use fork digest in gossip topic (leanSpec #622)

Change nlean's default --network value from "devnet0" to "12345678"
to match the fork digest gossipsub topic format defined in leanSpec
PR #622. All lean clients are adopting this change.

The --network flag is passed to nlean's GossipTopicProvider which
builds topics like /leanconsensus/{fork_digest}/block/ssz_snappy.

Author: GrapeBaBa

client-cmds/nlean-cmd.sh

@@ -7,7 +7,7 @@
 # Default assumes sibling checkouts: <workspace>/nlean and <workspace>/lean-quickstart.
 nlean_repo="${NLEAN_REPO:-$scriptDir/../nlean}"
 nlean_docker_image="${NLEAN_DOCKER_IMAGE:-ghcr.io/nleaneth/nlean:devnet4}"
-nlean_network_name="${NLEAN_NETWORK_NAME:-devnet0}"
+nlean_network_name="${NLEAN_NETWORK_NAME:-12345678}"
 log_level="${NLEAN_LOG_LEVEL:-}"
 enable_metrics="${enableMetrics:-false}"
 
@@ -17,7 +17,7 @@ if [[ "$enable_metrics" != "true" && "$enable_metrics" != "false" ]]; then
 fi
 
 if [[ -z "${nlean_network_name// }" ]]; then
-  nlean_network_name="devnet0"
+  nlean_network_name="12345678"
 fi
 
 log_level="${log_level#${log_level%%[![:space:]]*}}"