fix(@angular-devkit/build-angular): support ESNext as target for JavaScript optimizations

Previously, when ESNext was used, we fallbacked to ES2020 which caused ESBuild to output broken code.

Closes #22486

(cherry picked from commit b5c4a23)

Author: alan-agius4

Diff for: packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-plugin.ts

@@ -156,12 +156,12 @@ export class JavaScriptOptimizerPlugin {
           if (this.options.target) {
             if (this.options.target <= ScriptTarget.ES5) {
               target = 5;
-            } else if (this.options.target < ScriptTarget.ESNext) {
+            } else if (this.options.target === ScriptTarget.ESNext) {
+              target = 'next';
+            } else {
               target = Number(
                 ScriptTarget[this.options.target].slice(2),
               ) as OptimizeRequestOptions['target'];
-            } else {
-              target = 2020;
             }
           }
 

Diff for: packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-worker.ts

@@ -48,7 +48,7 @@ export interface OptimizeRequestOptions {
   /**
    * Specifies the target ECMAScript version for the output code.
    */
-  target: 5 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020;
+  target: 5 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 'next';
   /**
    * Controls whether esbuild should only use the WASM-variant instead of trying to
    * use the native variant. Some platforms may not support the native-variant and
@@ -105,7 +105,8 @@ export default async function ({ asset, options }: OptimizeRequest) {
     asset.name,
     esbuildResult.code,
     options.sourcemap,
-    options.target,
+    // Terser only supports up to ES2020.
+    options.target === 'next' ? 2020 : options.target,
     options.advanced,
   );
 
@@ -208,7 +209,7 @@ async function optimizeWithTerser(
   name: string,
   code: string,
   sourcemaps: boolean | undefined,
-  target: OptimizeRequest['options']['target'],
+  target: Exclude<OptimizeRequest['options']['target'], 'next'>,
   advanced: boolean | undefined,
 ): Promise<{ code: string; map?: object }> {
   const result = await minify(