worker: improve integration with native addons

Allow loading add-ons from multiple Node.js instances if they are
declared context-aware; in particular, this applies to N-API addons.

Also, plug a memory leak that occurred when registering N-API addons.

Refs: https://github.com/nodejs/node/pull/23319

PR-URL: https://github.com/nodejs/node/pull/26175
Fixes: https://github.com/nodejs/node/issues/21481
Fixes: https://github.com/nodejs/node/issues/21783
Fixes: https://github.com/nodejs/node/issues/25662
Fixes: https://github.com/nodejs/node/issues/20239
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

test/node-api/test_worker_terminate/test.js

@@ -4,6 +4,11 @@ const assert = require('assert');
 const { Worker, isMainThread, workerData } = require('worker_threads');
 
 if (isMainThread) {
+  // Load the addon in the main thread first.
+  // This checks that N-API addons can be loaded from multiple contexts
+  // when they are not loaded through NAPI_MODULE().
+  require(`./build/${common.buildType}/test_worker_terminate`);
+
   const counter = new Int32Array(new SharedArrayBuffer(4));
   const worker = new Worker(__filename, { workerData: { counter } });
   worker.on('exit', common.mustCall(() => {

test/node-api/test_worker_terminate/test_worker_terminate.c

@@ -36,4 +36,6 @@ napi_value Init(napi_env env, napi_value exports) {
   return exports;
 }
 
+// Do not start using NAPI_MODULE_INIT() here, so that we can test
+// compatibility of Workers with NAPI_MODULE().
 NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)