Show rolled up dates on epic route

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/160871



Merged-by: Alexandru Croitor <acroitor@gitlab.com>
Approved-by: Kassio Borges <kborges@gitlab.com>
Approved-by: Alexandru Croitor <acroitor@gitlab.com>
Co-authored-by: Nicolas Dular <ndular@gitlab.com>