refactor(compiler-cli): export ExtendedTemplateCheckerImpl and template checks (#43107)

This commit exports the implementation of `ExtendedTemplateChecker` to
generate extended template diagnostics and all the template checks.

Refs #42966

PR Close #43107

packages/compiler-cli/src/ngtsc/typecheck/extended/index.ts

@@ -0,0 +1,9 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+export {ExtendedTemplateCheckerImpl} from './src/extended_template_checker';