Add Owners to available options in 'Allowed to create projects' list on Group

Proposal

I would like to be able to set Owners under the Allowed to create projects setting on a group.

We configure our projects via Terraform, and don't want our members creating projects outside of our terraform configuration. We can configure the project creation level on groups, but the values are Maintainers, Developers + Maintainers, or No One. When setting to No One, our terraform is unable to create projects because this really means no one 😄 However, if we set it to Maintainers, members in the group that are Maintainers are able to create projects manually, outside of our terraform. Again, this is not desired. I would like to see Owners be allowed in the list, so we can say only Owners are allowed to create projects in a group. I see Owners in the list for Allowed to create subgroups, so it seems like a natural fit to let Owners be an option in the Allowed to create projects setting.

Implementation guide

• The options are defined by https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/api/helpers/groups_helpers.rb#L20 with a similar option for projects just above.
• It may be as simple as adjusting the option values defined in https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/access.rb as referenced by the GroupsHelper.