Such injectables were not appearing in the providers lists of their NgModule. This commit updates the doc-gen to support associating these automatically. Further, it also allows developers to mark other injectables that are provided in an NgModule with a reference to the NgModule where they are provided. The commit also does a refactoring of the `processNgModuleDocs` dgeni processor code, to make it easier to maintain. Fixes #41203 PR Close #41960