fix(@angular-devkit/build-angular): enable custom es2020 and `es201…

…5` conditional exports

By adding the `es2020` and `es2015` condition names, the build process will now use ES2020 or ES2015 specific files if a package's exports entries contain files for either of those conditions. This allows packages to provide multiple variants of the code that the bundler can then use based on the bundler's configuration. As of Angular v13, ES2020 code is preferred. However, some packages may prefer to export other variants by default but provide an `es2020`/`es2015` condition to allow other variants if requested.
The server configuration is intentional not altered since the server output executes on Node.js and should use the `node` condition which is automatically added by Webpack based on the output target.

packages/angular_devkit/build_angular/src/builders/browser/specs/lazy-module_spec.ts

@@ -165,8 +165,6 @@ describe('Browser Builder lazy modules', () => {
     const { files } = await browserBuild(architect, host, target, { commonChunk: false });
     expect(files['src_one_ts.js']).not.toBeUndefined();
     expect(files['src_two_ts.js']).not.toBeUndefined();
-    expect(
-      files['default-node_modules_angular_common___ivy_ngcc___fesm2015_http_js.js'],
-    ).toBeUndefined();
+    expect(files['default-node_modules_angular_common_fesm2020_http_mjs.js']).toBeUndefined();
   });
 });

packages/angular_devkit/build_angular/src/webpack/configs/browser.ts

@@ -55,6 +55,7 @@ export function getBrowserConfig(wco: WebpackConfigOptions): webpack.Configurati
     devtool: false,
     resolve: {
       mainFields: ['es2020', 'es2015', 'browser', 'module', 'main'],
+      conditionNames: ['es2020', 'es2015', '...'],
     },
     output: {
       crossOriginLoading,

packages/angular_devkit/build_angular/src/webpack/configs/test.ts

@@ -55,6 +55,7 @@ export function getTestConfig(
     target: wco.tsConfig.options.target === ScriptTarget.ES5 ? ['web', 'es5'] : 'web',
     resolve: {
       mainFields: ['es2020', 'es2015', 'browser', 'module', 'main'],
+      conditionNames: ['es2020', 'es2015', '...'],
     },
     devtool: false,
     entry: {