Return empty entries on split

[Erik-White]

The behaviour of the ReadOnlySpan<char> split extensions methods in SpanSplitExtensions differ from the .NET string split methods. The behaviour should be aligned to standard .NET implementation, see https://github.com/Microsoft/referencesource/blob/master/mscorlib/system/string.cs#L1010

This can easily be demonstrated:

Console.WriteLine(string.Empty.Split('/').Count());
>> 1
Console.WriteLine(string.Empty.AsMemory().Split('/').Count());
>> 0

[Olof-Lagerkvist]

Good find, thanks a lot!
Yes I agree that the behavior should be as close as possible to String.Split behavior to make migration easier.