fix(ngcc): handle entry-points within container folders (#36305)

The previous optimizations in #35756 to the
`DirectoryWalkerEntryPointFinder` were over zealous
with regard to packages that have entry-points stored
in "container" directories in the package, where the
container directory was not an entry-point itself.

Now we will also walk such "container" folders as long
as they do not contain `.js` files, which we regard as an
indicator that the directory will not contain entry-points.

Fixes #36216

PR Close #36305

packages/compiler-cli/ngcc/src/entry_point_finder/directory_walker_entry_point_finder.ts

@@ -156,12 +156,21 @@ export class DirectoryWalkerEntryPointFinder implements EntryPointFinder {
         isEntryPoint = true;
       }
 
-      if (!isDirectory || !isEntryPoint) {
+      if (!isDirectory) {
-        // This path is not an entry-point directory so we are done
+        // This path is not a directory so we are done.
         continue;
       }
 
+      // This directory may contain entry-points of its own.
       const childPaths = this.fs.readdir(absolutePath);
+      if (!isEntryPoint &&
+          childPaths.some(
+              childPath => childPath.endsWith('.js') &&
+                  this.fs.stat(this.fs.resolve(absolutePath, childPath)).isFile())) {
+        // We do not consider non-entry-point directories that contain JS files as they are very
+        // unlikely to be containers for sub-entry-points.
+        continue;
+      }
       this.collectSecondaryEntryPoints(entryPoints, packagePath, absolutePath, childPaths);
     }
   }

packages/compiler-cli/ngcc/test/entry_point_finder/directory_walker_entry_point_finder_spec.ts

@@ -287,6 +287,22 @@ runInEachFileSystem(() => {
         expect(entryPoints).toEqual([]);
       });
 
+      it('should process sub-entry-points within a non-entry-point containing folder in a package',
+         () => {
+           const basePath = _Abs('/containing_folders/node_modules');
+           loadTestFiles([
+             ...createPackage(basePath, 'package'),
+             ...createPackage(fs.resolve(basePath, 'package/container'), 'entry-point-1'),
+           ]);
+           const finder = new DirectoryWalkerEntryPointFinder(
+               fs, config, logger, resolver, manifest, basePath, undefined);
+           const {entryPoints} = finder.findEntryPoints();
+           expect(dumpEntryPointPaths(basePath, entryPoints)).toEqual([
+             ['package', 'package'],
+             ['package', 'package/container/entry-point-1'],
+           ]);
+         });
+
       it('should handle dependencies via pathMappings', () => {
         const basePath = _Abs('/path_mapped/node_modules');
         const pathMappings: PathMappings = {