Do not report MA0005 for arrays of pointers

[meziantou]

Problem

MA0005 reported zero-length arrays of pointers, and its code fix produced code that does not compile:

public unsafe class Sample
{
    public static int*[] Run() => new int*[0];
}

became

public static int*[] Run() => System.Array.Empty<int*>(); // CS0306

Pointer and function pointer types cannot be used as generic type arguments.

Change

• UseArrayEmptyAnalyzer no longer reports when the array's element type is a pointer or a function pointer. The code fix only runs on this diagnostic, so it is no longer offered either.
• Arrays whose element type is itself an array of pointers (new int*[0][]) are still reported, since Array.Empty<int*[]>() is valid.
• docs/Rules/MA0005.md documents the exclusion.

Tests

• EmptyPointerArray_ShouldNotReportError: new int*[0], new int*[] { }, new delegate*<void>[0]
• EmptyArrayOfPointerArrays_ShouldReportError: new int*[0][] is still fixed to System.Array.Empty<int*[]>()

All 12 UseArrayEmptyAnalyzerTests pass on Roslyn 5.9 and 4.8. With the analyzer change reverted, the three pointer cases fail. I ran only these tests locally; CI runs the other Roslyn versions.