feat: replace vscodeipc with vscodessh (#5645)

The VS Code extension has been refactored to use VS Code
Remote SSH instead of using the private API.

This changes the structure to continue using SSH, but
output network information periodically to a file.

agent/agent.go

@@ -304,7 +304,18 @@ func (a *agent) createTailnet(ctx context.Context, derpMap *tailcfg.DERPMap) (_
 			if err != nil {
 				return
 			}
-			go a.sshServer.HandleConn(conn)
+			closed := make(chan struct{})
+			_ = a.trackConnGoroutine(func() {
+				select {
+				case <-network.Closed():
+				case <-closed:
+				}
+				_ = conn.Close()
+			})
+			_ = a.trackConnGoroutine(func() {
+				defer close(closed)
+				a.sshServer.HandleConn(conn)
+			})
 		}
 	}); err != nil {
 		return nil, err