Add trim/AOT annotations to WinUI XAML behaviors

[Sergio0694]

This PR introduces the following changes:

• Update the .NET TFM from .NET 5 to .NET 8
  • .NET 5 is EOL, .NET 6 is going to be EOL in a few months, .NET 8 has gone GA for over a year already now
  • We also need .NET 8 to be able to set IsAotCompatible
• Bump WASDK dependency to latest stable
• Add trim/AOT annotations to the XAML behaviors projects

[azchohfi]

LGTM. Just needs to bump the version and make sure our build/release process is going to work fine with net8. We'll likely need to update our ADO build.

[mgoertz-msft]