Updated .NET Crypto Shredding example to .NET 6, bumped packages to the latest version

[oskardudycz]

• Updated .NET CQRS flow to .NET 6, bumped packages to the latest version
• Moved to file-scoped namespaces.
• Updated obsolete usage of AesManaged to Aes.Create. From: https://www.meziantou.net/cryptography-in-dotnet.htm#aes:

  "AESManaged is fully implemented in .NET, however, the implementation is not FIPS compliant. AESCryptoServiceProvider uses the Windows implementation (CryptoAPI) which is FIPS compliant. Or you can create an instance of the best available provider using AES.Create()."

Note for reviewers: Review with whitespace hidden, there is ten time less line change https://github.com/EventStore/samples/pull/13/files?diff=split&w=1