Update the UserAgent to align with industry standard naming

- The industry standard for agent names is to prefix and subfix with / to seperate sections of the agent.
- As we are optimizing and preparing for a good Bitcoin compatible node, this was decided to change from the previous format.

Author: sondreb

src/Blockcore/Connection/ConnectionManager.cs

@@ -134,7 +134,7 @@ public ConnectionManager(IDateTimeProvider dateTimeProvider,
             this.disconnectedPerfCounter = new PerformanceCounter();
 
             this.Parameters.Version = this.NodeSettings.Network.Consensus.ConsensusFactory.Protocol.ProtocolVersion;
-            this.Parameters.UserAgent = $"{this.ConnectionSettings.Agent}:{versionProvider.GetVersion()}({this.Network.CoinTicker};{this.Parameters.Version})";
+            this.Parameters.UserAgent = $"/{this.ConnectionSettings.Agent}:{versionProvider.GetVersion()}({this.Network.CoinTicker};{this.Parameters.Version})/";
 
             nodeStats.RegisterStats(this.AddComponentStats, StatsType.Component, this.GetType().Name, 1100);
         }