This is intended to be a new major release of DiffLib,
written in .NET 8, C# 12, hopefully with major performance improvements, based on new
types, such as Span<T> and similar.
Current status of project is "on hold". (ReadOnly)Span<T> is severely limited when dealing with recursive algorithms,
as there is no way to cache intermediate results.
A recursive enumerator can easily keep state like this, but since the entire stack unwinds and all local spans are discarded, and cannot be temporarily stored between invocations, it seems I need a completely new way to think about this recursive algorithm for this to work.