Counts fetched and imported Github objects by project and globally. This
is done using the `Gitlab::GithubImport::ObjectCounter`.

These counts will provide information to follow the stability of the
Github Importer on Grafana.

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/335199

MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/65700
Changelog: changed