Thunder installs all optional config after a module install

Problem/Motivation

In thunder_modules_installed there is a call on \Drupal::service('config.installer')->installOptionalConfig();.

We added that to the following use-case:
If you uninstall e.g. media_entity_instagram and reinstall it, all the media_entity_instagram configs should be installed again.

Proposed resolution

Remove the installOptionalConfig() calls and fix it in core.

Remaining tasks

User interface changes

API changes

Data model changes