Allow module reinstall

[zackdavies]

Adding enforced dependencies to config files to allow reinstallation - see here: #370

[ekes]

localgovdrupal/localgov#762 (comment)

How much does directories keep on working when you uninstall it, but keep all the config in place? Is it possible someone is wanting to do this? Do we want to support it?

[stephen-cox]

For this to fully fix the issue described in #370 it also needs to add an enforced dependency to all the submodules in the modules directory.

[stephen-cox]

Further to my comment above, you are not prevented from uninstalling Directories if directory content exists, leaving phantom content which throws errors if you try to access it. We'll need to address this first localgovdrupal/localgov#762

[finnlewis]

Interesting! I think we'll need to test this a bit more.

[finnlewis]

Discussing in Merge Tuesday, looking at the suggestion from @millnut on localgovdrupal/localgov#762 (comment)

We could look at creating a module uninstall validator using the Drupal\Core\Extension\ModuleUninstallValidatorInterface and inform the users that the module cannot be uninstalled as content exists for the news content type. This way it's a user decision to remove all the content before uninstalling the module.

We think we want to follow this, and write a validation to prevent uninstalling until the content has been deleted.