Inbox Windows Forms analyzers into Windows Desktop SDK as per
https://github.com/dotnet/designs/blob/main/accepted/2021/InboxSourceGenerators.md

The analyzers and source generators come from a Windows Forms transport
package built and packaged by https://github.com/dotnet/winforms/tree/main/pkg/Microsoft.Private.Winforms
project. The analyzers are placed under .\sdk\analyzers folder, so that
when the transport package is ingested the analyzers would not get imported
by the ingesting projects (e.g. this project or dotnet/wpf).

Add validation to verify the Windows Forms transport package contains the
required content.

And while at it, update the way the Windows Forms file classifications
are referenced.

Microsoft.DotNet.Wpf.GitHub , Microsoft.DotNet.Wpf.ProjectTemplates , Microsoft.NET.Sdk.WindowsDesktop
 From Version 6.0.0-rc.1.21378.4 -> To Version 6.0.0-rc.1.21378.6

Dependency coherency updates

Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Private.Winforms,Microsoft.Dotnet.WinForms.ProjectTemplates
 From Version 6.0.0-rc.1.21378.3 -> To Version 6.0.0-rc.1.21378.7 (parent: Microsoft.DotNet.Wpf.GitHub

…7-607a64fca6a0' into inbox_Windows_Forms_analyzers