feat: support .NET 8.0 | Remove BinaryFormatter from `TestingExcept…

…ion` (#383)

- #381 

Remove `BinaryFormatter` and serialization support for
`TestingException` as the [`BinaryFormatter` becomes
obsolete](https://github.com/dotnet/designs/blob/main/accepted/2020/better-obsoletion/binaryformatter-obsoletion.md)

Source/Testably.Abstractions.Testing/FileSystemInitializer/TestingException.cs

@@ -26,6 +26,7 @@ public TestingException(string message, Exception inner)
 	{
 	}
 
+#if !NET8_0_OR_GREATER
 	/// <summary>
 	///     Initializes a new instance of <see cref="TestingException" /> for serialization.
 	///     <para />
@@ -35,4 +36,5 @@ protected TestingException(SerializationInfo info, StreamingContext context)
 		: base(info, context)
 	{
 	}
+#endif
 }

Tests/Testably.Abstractions.Testing.Tests/FileSystemInitializer/TestingExceptionTests.cs

@@ -1,4 +1,5 @@
-using System.IO;
+#if !NET8_0_OR_GREATER
+using System.IO;
 using System.Runtime.Serialization.Formatters.Binary;
 using Testably.Abstractions.Testing.FileSystemInitializer;
 
@@ -18,15 +19,16 @@ public void
 		byte[] buffer = new byte[4096];
 		using MemoryStream ms = new(buffer);
 		using MemoryStream ms2 = new(buffer);
+#pragma warning disable SYSLIB0011 //BinaryFormatter serialization is obsolete - only used in unit test
 		BinaryFormatter formatter = new();
-		#pragma warning disable SYSLIB0011 //BinaryFormatter serialization is obsolete - only used in unit test
 		formatter.Serialize(ms, originalException);
 		TestingException deserializedException =
 			(TestingException)formatter.Deserialize(ms2);
-		#pragma warning restore SYSLIB0011
+#pragma warning restore SYSLIB0011
 
 		Assert.Equal(originalException.InnerException?.Message,
 			deserializedException.InnerException?.Message);
 		Assert.Equal(originalException.Message, deserializedException.Message);
 	}
 }
+#endif