feat(ngcc): support for new APF where module points to esm2015 output (#36944)

As of version 10, libraries following the APF will no longer contain
ESM5 output. Hence, tests in ngcc need to be updated as they currently
rely on the release output of `@angular/core`.

Additionally, we'd need to support in ngcc that the `module`
property of entry-points no longer necessarily refers to
`esm5` output, but instead can also target `esm2015`.

We currently achieve this by checking the path the `module`
property points to. We can do this because as per APF, the
folder name is known for the esm2015 output. Long-term for
more coverage, we want to sniff the format by looking for
known ES2015 constructs in the file `module` refers to.

PR Close #36944

packages/compiler-cli/ngcc/test/packages/entry_point_spec.ts

@@ -429,6 +429,12 @@ runInEachFileSystem(() => {
       expect(getEntryPointFormat(fs, entryPoint, 'module')).toBe('esm5');
     });
 
+    it('should return `esm2015` format for `module` property if it points to esm2015 output',
+       () => {
+         entryPoint.packageJson['module'] = '../fesm2015/valid-entry-point.js';
+         expect(getEntryPointFormat(fs, entryPoint, 'module')).toBe('esm2015');
+       });
+
     (['browser', 'main'] as EntryPointJsonProperty[]).forEach(browserOrMain => {
       it('should return `esm5` for `' + browserOrMain +
              '` if the file contains import or export statements',