parallelizes gossip packets receiver with processing of requests (#17647)

Gossip packet processing is composed of two stages:
  * The first is consuming packets from the socket, deserializing,
    sanitizing and verifying them:
    https://github.com/solana-labs/solana/blob/7f0349b29/gossip/src/cluster_info.rs#L2510-L2521
  * The second is actually processing the requests/messages:
    https://github.com/solana-labs/solana/blob/7f0349b29/gossip/src/cluster_info.rs#L2585-L2605

The former does not acquire any locks and so can be parallelized with
the later, allowing better pipelineing properties and smaller latency in
responding to gossip requests or propagating messages.

gossip/src/cluster_info_metrics.rs

@@ -118,6 +118,7 @@ pub(crate) struct GossipStats {
     pub(crate) trim_crds_table_failed: Counter,
     pub(crate) trim_crds_table_purged_values_count: Counter,
     pub(crate) tvu_peers: Counter,
+    pub(crate) verify_gossip_packets_time: Counter,
 }
 
 pub(crate) fn submit_gossip_stats(
@@ -171,6 +172,11 @@ pub(crate) fn submit_gossip_stats(
             stats.process_gossip_packets_time.clear(),
             i64
         ),
+        (
+            "verify_gossip_packets_time",
+            stats.verify_gossip_packets_time.clear(),
+            i64
+        ),
         (
             "handle_batch_ping_messages_time",
             stats.handle_batch_ping_messages_time.clear(),