Allow self assignable roles and make role groups

For the self assignable roles, I feel this is pretty self explanatory. Members would be able to assign a role that is self-assignable to themselves without having the “MANAGE_ROLES” permission. For the role groups, I think this would be very helpful for the self assignable when members want to only be allowed to choose 1 or 2 roles (such as pronoun roles) and not have members choose all of the roles. It would also work somewhat like channel categories where you could sync the permissions of roles to the groups perms.