This change introduces four sets of extension methods with overloads:

- OrderAsArray(...)
- OrderDescendingAsArray(...)
- OrderByAsArray(...)
- OrderByDescendingAsArray(...)

Each of these operates on an `ImmutableArray<T>` and returns an `ImmutableArray<T>`.

1. Don't sort if the array has zero or 1 element.
2. Don't sort if the array or the keys are already ordered.
3. Avoid creating an `IComparer<T>` until its time to actually sort

Add tests for Comparison<T> overloads