Rebex MSG for .NET R6.0

Adds new set of binaries targeting the final version of .NET 6.0.

Features

• All: Added a new set of binaries targeting Microsoft .NET 6.0. Including:
  • Microsoft Windows (x64, x86, ARM64).
  • Linux (x64, ARM32, ARM64).
  • Apple macOS (x64).
• All: Removed several obsolete and deprecated APIs.
• All: Removed support for legacy ISerializable interface from binaries for Microsoft .NET Standard.
• MIME: Changed default charset for MIME text entities to UTF-8.