Bug: Empty Array is projected as null instead of an array of length 0

Description

Consider the idl:

String[] GetItems();

If the implementation of this function returns an empty array, the CsWinRT projection will return null. But it is expected to return a non-null empty array.

The downside of empty arrays being projected as null is that it forces the consumer to write unnatural code:

string[] items = thing.GetItems();
if (items != null)
{
    foreach (var item in items)
    {
        Console.WriteLine(item);
    }
}

instead of the more idiomatic:

foreach (var item in thing.GetItems())
{
    Console.WriteLine(item);
}

@oldnewthing as FYI.

Steps To Reproduce

See description.

Expected Behavior

See description.

Version Info

2.2.0

Additional Context

No response

Start by reproducing the String[] GetItems() case described in the issue with an implementation that returns an empty array, then trace the CsWinRT projection path that produces the C# result. Done means an empty projected result is non-null, has length 0, and supports direct enumeration without a null check.