Since migrations are not run by new instances, add a production
fixture that should ensure that the self-monitoring project is created
for new instances as well.

Adding, destroying and toggling emoji previously lacked services and
instead were performed through methods called on Awardable models.

This led to inconsistencies where relevant todos would be marked as done
only when emoji were awarded through our controllers, but not through
the API. Todos could also be marked as done when an emoji was being
removed.

Behaviour changes

- Awarding emoji through the API will now mark a relevant Todo as done
- Toggling an emoji off (destroying it) through our controllers will no
  longer mark a relevant Todo as done

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/63372

These will be moved to the EE codebase.

We also scope the `rescue`s to only those raised by ActiveRecord, which
would have allowed us to spot this logic error sooner.

In order to avoid confusion between Gitlab::Importers module and other
like named modules, this renamed it to Gitlab::DatabaseImporters.

Remove CommonMetricsImporter patch and change all references to
CommonMetrics::Importer. Move specs into their appropriate folders. Also
cleans up some common_metric importer namespacing.