feat(api/gitlab/v1): add last published timestamp to get repository details response

mentioned in commit 4da5b7c3

mentioned in issue #1235 (closed)

mentioned in merge request gitlab-com/gl-infra/k8s-workloads/gitlab-com!3501 (merged)

mentioned in merge request gitlab-com/gl-infra/k8s-workloads/gitlab-com!3502 (merged)

mentioned in merge request gitlab-com/gl-infra/k8s-workloads/gitlab-com!3503 (merged)

mentioned in merge request omnibus-gitlab!7508 (merged)

mentioned in merge request gitlab-org/charts/gitlab!3688 (merged)