Replace symlinks with meta/runtime.yml redirects. (#4562)

CONTRIBUTING.md

@@ -106,9 +106,15 @@ Creating new modules and plugins requires a bit more work than other Pull Reques
    - Make sure that new plugins and modules have tests (unit tests, integration tests, or both); it is preferable to have some tests
      which run in CI.
 
-4. For modules and action plugins, make sure to create your module/plugin in the correct subdirectory, and create a symbolic link
-   from `plugins/modules/` respectively `plugins/action/` to the actual module/plugin code. (Other plugin types should not use
-   subdirectories.)
+4. For modules and action plugins, make sure to create your module/plugin in the correct subdirectory, and add a redirect entry
+   in `meta/runtime.yml`. For example, for the `aerospike_migrations` module located in
+   `plugins/modules/database/aerospike/aerospike_migrations.py`, you need to create the following entry:
+   ```.yaml
+       aerospike_migrations:
+         redirect: community.general.database.aerospike.aerospike_migrations
+   ```
+   Here, the relative path `database/aerospike/` is inserted into the module's FQCN (Fully Qualified Collection Name) after the
+   collection's name and before the module's name. This must not be done for other plugin types but modules and action plugins!
 
    - Action plugins need to be accompanied by a module, even if the module file only contains documentation
      (`DOCUMENTATION`, `EXAMPLES` and `RETURN`). The module must have the same name and directory path in `plugins/modules/`