fix(@angular-devkit/build-angular): avoid implicit CSS file extensions when resolving

Unlike the non-ESM Node.js resolution for JS files, CSS does not have the concept
of implicit file extensions. To avoid incorrectly resolving a file as CSS,
stylesheet bundling no longer attempts to resolve implicit extensions. Preprocessors,
such as Sass, contain logic internally that handles any specific resolution cases
for their respective preprocessor and such behavior is unaffected.

Author: clydin

packages/angular_devkit/build_angular/src/tools/esbuild/stylesheets/bundle-options.ts

@@ -84,6 +84,9 @@ export function createStylesheetBundleOptions(
     publicPath: options.publicPath,
     conditions: ['style', 'sass', 'less'],
     mainFields: ['style', 'sass'],
+    // Unlike JS, CSS does not have implicit file extensions in the general case.
+    // Preprocessor specific behavior is handled in each stylesheet language plugin.
+    resolveExtensions: [],
     plugins,
   };
 }