Port System.Linq enhancements added in .NET 6 to System.Linq.Async

It seems that the [LINQ enhancements](https://devblogs.microsoft.com/dotnet/announcing-net-6/#system-linq-distinctby-unionby-intersectby-exceptby) added in .NET 6 to `System.Linq` have not been made available to `System.Linq.Async`. Some of them probably don't make much sense - e.g. `TryGetNonEnumeratedCount`, but others such as `Chunk`, the `*By` (DistinctBy/UnionBy/IntersectBy/ExceptBy/MinBy/MaxBy) methods and `*OrDefault` (FirstOrDefault/LastOrDefault/SingleOrDefault) overloads that take a default value are quite useful and I sometimes miss them when using async streams.

Could we add these enhancements to `System.Linq.Async` as well? If anything, it would allow the async streams to achieve feature parity with `IEnumerable` which I guess would be a valid argument in and by itself?