.NET 6 Linq Improvements: MaxBy and MinBy

A small but frequent annoyance in LINQ was finding the object with the max value. Previously, we had doing `OrderByDescending(x => x.Val).First()`, which is O(N log N).

.NET 6 adds `MaxBy` and `MinBy`.

var mostExpensiveProduct = products.MaxBy(p => p.Price);

This is O(N) and much more readable. Other additions include `Chunk()` for splitting lists into batches.