BinaryFormatter is disabled in WinForms or WPF projects in preview6

Describe the bug

The intent behind this change - https://github.com/dotnet/sdk/commit/ccfcbe828cda905f1f995f63f26485dd9a7a7dd5 was that projects with these properties

    <UseWindowsForms>true</UseWindowsForms>
    <UseWPF>true</UseWPF>

Have BinaryFormatter.Serialize/Deserialize methods enabled in .NET8. However in SDK Preview6, we are getting a NotSupportedException

To Reproduce

1. Install the latest SDK
2. Create a winforms application targeting .NET 8 in the VS (app is here https://github.com/Tanya-Solyanik/Repro)
3. Add <NoWarn>SYSLIB0011</NoWarn> to the project file
4. Add a call to BinaryFormatter.Serialize()
5. Run that code

Result: System.NotSupportedException: BinaryFormatter serialization and deserialization are disabled within this application. See https://aka.ms/binaryformatter for more information. at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph) at WinFormsApp29.Form1.button1_Click(Object sender, EventArgs e) in C:\Users\tanyaso\source\repos\WinFormsApp29\WinFormsApp29\Form1.cs:line 17

Further technical details

• Repros both in the VS and on the command line, as long as SDK preview 6.23280 is installed
• If I add a switch

            AppContext.SetSwitch(
                "System.Runtime.Serialization.EnableUnsafeBinaryFormatterSerialization",
                isEnabled: true);

or <EnableUnsafeBinaryFormatterSerialization>true</EnableUnsafeBinaryFormatterSerialization> BinaryFormatter serializes successfully.

[Amy-Li03]

Verified issue https://github.com/microsoft/winforms-designer/issues/5233 on .NET SDK 8.0.100-preview.5.23301.12 test pass build, it was fixed. In winforms VB project, ‘Explorer Form’ template form designer(contains ImageList) can be loaded successfully.

[GrabYourPitchforks]

This appears to be a regression from 8.0 Preview 4, where the scenario worked correctly. I’m trying to narrow down the change.