Copy assets from appropriate directory for kbn-monaco (#178669)

## Summary Closes #178448 Per the configuration in kibana, Monaco by default will attempt to load the specific worker for each language using the public path record defined on `window.__kbnPublicPath__` [see here](https://github.com/elastic/kibana/blob/main/packages/kbn-monaco/src/register_globals.ts#L42) but an error occurs whilst attempting to request the script at the url we expect it to be at because it doesn't exist there, as seen here; <img width="1071" alt="Screenshot 2024-03-13 at 17 21 36" src="https://github.com/elastic/kibana/assets/7893459/012dd841-ba5c-4744-bb32-708bc6efc976"> Ideally this works but with the current setup for CDN assets it doesn't map 1:1 to how the assets are expected, we should be copying from the directory `target_workers` to match the same definition for [building packages ](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/build_packages_task.ts#L111-L113), similar to what we have [here](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/create_cdn_assets_task.ts#L67-L74) which is what this PR introduces. The hypothesis above is verifiable by attempting to request the same resource on the same build of the deployment where the error is reported, with the `target_workers` path prepended, like so https://kibana.estccdn.com/552e8adcca05/bundles/kbn-monaco/target_workers/json.editor.worker.js we get the file.  --------- Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
elastic · Mar 21, 2024 · bb54184 · bb54184
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diff --git a/NOTICE.txt b/NOTICE.txt
@@ -1,6 +1,31 @@
 Kibana source code with Kibana X-Pack source code
 Copyright 2012-2024 Elasticsearch B.V.
 
+---
+Adapted from remote-web-worker, which was available under a "MIT" license.
+
+MIT License (MIT)
+
+Copyright (c) 2022 Jan Nicklas
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
 ---
 Pretty handling of logarithmic axes.
 Copyright (c) 2007-2014 IOLA and Ole Laursen.

diff --git a/packages/kbn-test/src/jest/setup/polyfills.jsdom.js b/packages/kbn-test/src/jest/setup/polyfills.jsdom.js
@@ -32,3 +32,18 @@ global.Blob = require('blob-polyfill').Blob;
 if (!global.hasOwnProperty('ResizeObserver')) {
   global.ResizeObserver = require('resize-observer-polyfill');
 }
+
+if (!global.hasOwnProperty('Worker')) {
+  class Worker {
+    constructor(stringUrl) {
+      this.url = stringUrl;
+      this.onmessage = () => {};
+    }
+
+    postMessage(msg) {
+      this.onmessage(msg);
+    }
+  }
+
+  global.Worker = Worker;
+}
diff --git a/packages/kbn-ui-shared-deps-src/src/polyfills.js b/packages/kbn-ui-shared-deps-src/src/polyfills.js
@@ -17,3 +17,85 @@ if (typeof window.Event === 'object') {
 
 require('whatwg-fetch');
 require('symbol-observable');
+
+/* @notice
+ *
+ * Adapted from remote-web-worker, which was available under a "MIT" license.
+ *
+ * MIT License (MIT)
+ *
+ * Copyright (c) 2022 Jan Nicklas
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+typeof window !== 'undefined' &&
+  // eslint-disable-next-line no-global-assign
+  (Worker = ((BaseWorker) =>
+    class Worker extends BaseWorker {
+      constructor(url, options) {
+        let scriptUrl = String(url);
+        let objectURLRef;
+
+        try {
+          const isCrossOrigin = (URLObject) =>
+            URLObject.protocol === 'https:' && URLObject.origin !== window.location.origin;
+
+          scriptUrl = isCrossOrigin(new URL(scriptUrl)) // to bootstrap the actual script to work around the same origin policy.
+            ? (objectURLRef = URL.createObjectURL(
+                new Blob(
+                  [
+                    // Replace the `importScripts` function with
+                    // a patched version that will resolve relative URLs
+                    // to the remote script URL.
+                    //
+                    // Without a patched `importScripts` Webpack 5 generated worker chunks will fail with the following error:
+                    //
+                    // Uncaught (in promise) DOMException: Failed to execute 'importScripts' on 'WorkerGlobalScope':
+                    // The script at 'http://some.domain/worker.1e0e1e0e.js' failed to load.
+                    //
+                    // For minification, the inlined variable names are single letters:
+                    // i = original importScripts
+                    // a = arguments
+                    // u = URL
+                    `importScripts=((i)=>(...a)=>i(...a.map((u)=>''+new URL(u,"${scriptUrl}"))))(importScripts);importScripts("${scriptUrl}");`,
+                  ],
+                  {
+                    type: 'text/javascript',
+                  }
+                )
+              ))
+            : scriptUrl;
+        } catch {
+          // provided url doesn't match the expectation for URL constructor, it will be used as is
+        }
+
+        super(scriptUrl, options);
+
+        this.addEventListener(
+          'message',
+          function revokeURL() {
+            if (objectURLRef) {
+              URL.revokeObjectURL(objectURLRef);
+              objectURLRef = null;
+            }
+          },
+          { once: true }
+        );
+      }
+    })(Worker));
diff --git a/src/dev/build/tasks/create_cdn_assets_task.ts b/src/dev/build/tasks/create_cdn_assets_task.ts
@@ -76,7 +76,10 @@ export const CreateCdnAssets: Task = {
       resolve(buildSource, 'node_modules/@kbn/core/target/public'),
       resolve(bundles, 'core')
     );
-    await copyAll(resolve(buildSource, 'node_modules/@kbn/monaco'), resolve(bundles, 'kbn-monaco'));
+    await copyAll(
+      resolve(buildSource, 'node_modules/@kbn/monaco/target_workers'),
+      resolve(bundles, 'kbn-monaco')
+    );
 
     // packages/core/apps/core-apps-server-internal/src/core_app.ts
     await copyAll(