Replacement for Microsoft.CodeAnalysis.Build.Tasks package

[rainersigwald]

It looks like after #78584 the Microsoft.CodeAnalysis.Build.Tasks package isn't getting published, which is breaking the MSBuild repo's use of it (to construct a more-up-to-date-than-the-LKG output directory using a newish Roslyn). That's causing https://github.com/dotnet/msbuild/pull/11877 to fail to restore.

Is there a replacement we can reference instead? None of the packages published in recent builds jump out at me.