feat(ngcc): migrate services that are missing @Injectable() (#33362)

A class that is provided as Angular service is required to have an
`@Injectable()` decorator so that the compiler generates its injectable
definition for the runtime. Applications are automatically migrated
using the "missing-injectable" schematic, however libraries built for
older version of Angular may not yet satisfy this requirement.

This commit ports the "missing-injectable" schematic to a migration that
is ran when ngcc is processing a library. This ensures that any service
that is provided from an NgModule or Directive/Component will have an
`@Injectable()` decorator.

PR Close #33362

packages/compiler-cli/ngcc/src/migrations/migration.ts

@@ -42,4 +42,20 @@ export interface MigrationHost {
    * @param decorator the decorator to inject.
    */
   injectSyntheticDecorator(clazz: ClassDeclaration, decorator: Decorator): void;
+
+  /**
+   * Retrieves all decorators that are associated with the class, including synthetic decorators
+   * that have been injected before.
+   * @param clazz the class for which all decorators are retrieved.
+   * @returns the list of the decorators, or null if the class was not decorated.
+   */
+  getAllDecorators(clazz: ClassDeclaration): Decorator[]|null;
+
+  /**
+   * Determines whether the provided class in within scope of the entry-point that is currently
+   * being compiled.
+   * @param clazz the class for which to determine whether it is within the current entry-point.
+   * @returns true if the file is part of the compiled entry-point, false otherwise.
+   */
+  isInScope(clazz: ClassDeclaration): boolean;
 }