Enable support for .NET 8.0

[vbreuss]

Adapt Testably.Abstractions to support .NET 8.0.

This makes the following changes necessary:

• refactor: prepare support for .NET 8.0 #388

1. Add new methods for IRandom
   feat: support .NET 8.0 | Add new methods for IRandom #387

   • GetItems
   • Shuffle

2. Add new methods for IZipFile
   feat: support .NET 8.0 | Add new methods for IZipFile #386
   CreateFromDirectory and ExtractToDirectory now also work with a Stream

3. Change Timer so that it no longer throws ObjectDisposedException after being disposed:
   feat: support .NET 8.0 | Timer no longer throws ObjectDisposedException #385
   (see this change for more details)

4. IFileInfo.CreateText now refreshes the internal cache of the FileInfo
   feat: support .NET 8.0 | Refresh cache on IFileInfo.CreateText #384

5. Remove BinaryFormatter and serialization support for TestingException as the BinaryFormatter becomes obsolete
   feat: support .NET 8.0 | Remove BinaryFormatter from TestingException #383

6. LastAccessTime is no longer updated for the source file when copying it on OSX.
   (see Clone files on OSX-like platforms when possible, instead of copying the whole file dotnet/runtime#79243 for more details)
   feat: support .NET 8.0 | LastAccessTime is no longer updated for the source file when copying it on OSX #382

• feat: enable support for .NET 8.0 #389