Reimplement serialization part of OpenXML with ZString.

[tonyqus]

          I'm checking if we can rewrite serialization part with https://github.com/Cysharp/ZString. 

According to nuget stats, this library looks popular.

I found this library via this post

Originally posted by @tonyqus in https://github.com/nissl-lab/npoi/issues/1095#issuecomment-1707670328