Translate GroupBy followed by Distinct without aggregate operators

[smitpatel]

        [ConditionalTheory]
        [MemberData(nameof(IsAsyncData))]
        public virtual Task GroupBy_with_orderby_take_skip_distinct_followed_by_group_key_projection(bool isAsync)
        {
            return AssertQuery<Order>(
                isAsync,
                os => os.GroupBy(o => o.CustomerID).OrderBy(g => g.Key).Take(5).Skip(3).Distinct().Select(g => g.Key),
                assertOrder: true,
                elementAsserter: GroupingAsserter<string, Order>(o => o.OrderID),
                entryCount: 31);
        }

[smitpatel]

On higher level, to translate correctly we also need to decide what exactly Distinct on IGroupings mean.