Add `Allowed to delete projects` setting for groups

Problem to solve

Currently, at the group level, we have the Allowed to create projects setting. It would be nice to have an Allowed to delete projects setting at the group level. This would allow group owners to let group members with a role of Maintainer delete projects.

Links / references

Customer ticket -> https://gitlab.zendesk.com/agent/tickets/100097 (internal use)

/cc @jeremy_