This commit is a follow up to
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/77236
and adds the group level counterpart to the existing
Project Access Token UI. Group Access Tokens can already be created
by instance administrators via rails console or users via GitLab
REST API but not yet on the UI itself. The new page allows group
owners to list, create and delete said tokens.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/214045

Changelog: added