Modify lighthouse_network gossip types to free the blobs (#4064)

* Modify blob topics

* add signedblol type

pubsun messages are signed

* improve subnet topic index

* improve display code

* fix parse code

---------

Co-authored-by: Pawan Dhananjay <pawandhananjay@gmail.com>

beacon_node/lighthouse_network/src/service/mod.rs

@@ -235,6 +235,7 @@ impl<AppReqId: ReqId, TSpec: EthSpec> Network<AppReqId, TSpec> {
                     possible_fork_digests,
                     ctx.chain_spec.attestation_subnet_count,
                     SYNC_COMMITTEE_SUBNET_COUNT,
+                    4, // TODO(pawan): get this from chainspec
                 ),
                 max_subscribed_topics: 200,
                 max_subscriptions_per_request: 150, // 148 in theory = (64 attestation + 4 sync committee + 6 core topics) * 2