cluster: move handle tracking out of utils

internal/cluster/utils.js exported a handles object, which was
used in a test. That test, test-cluster-disconnect-handles.js,
was removed in nodejs#12495. This
commit moves the handles object to the only file in the codebase
that still uses it.

PR-URL: nodejs#23131
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/cluster/master.js

@@ -7,7 +7,7 @@ const EventEmitter = require('events');
 const RoundRobinHandle = require('internal/cluster/round_robin_handle');
 const SharedHandle = require('internal/cluster/shared_handle');
 const Worker = require('internal/cluster/worker');
-const { internal, sendHelper, handles } = require('internal/cluster/utils');
+const { internal, sendHelper } = require('internal/cluster/utils');
 const { ERR_SOCKET_BAD_PORT } = require('internal/errors').codes;
 const keys = Object.keys;
 const cluster = new EventEmitter();
@@ -19,6 +19,7 @@ const [ minPort, maxPort ] = [ 1024, 65535 ];
 
 module.exports = cluster;
 
+const handles = new Map();
 cluster.isWorker = false;
 cluster.isMaster = true;
 cluster.Worker = Worker;

lib/internal/cluster/utils.js

@@ -3,8 +3,7 @@ const util = require('util');
 
 module.exports = {
   sendHelper,
-  internal,
-  handles: new Map() // Used in tests.
+  internal
 };
 
 const callbacks = new Map();