[META] Make use of module uninstall validators

In #2278017: When a content entity type providing module is uninstalled, the entities are not fully deleted, leaving broken reference a new way to add ModuleUninstallValidators has been introduced and implemented for its use case. Given that, we should leverage the new API for other cases also and convert existing solutions to it. Right now, there are multiple hook_system_info_alter() implementations that use it to conditionally make modules required - those need to be converted.

Issues:
todo:
- List all the hook_system_info_alter() implementations here and file issues for each.
- For communication the new API provide a change notice and point to a nice example implementation.