Deprecate and delete Microsoft.DotNet.Build.Tasks.Packaging from Arcade main

[ViktorHofer]

• This issue is blocking
• This issue is causing unreasonable pain

dotnet/runtime is steadily working towards using NuGet's Pack task to produce nupkgs (and the corresponding symbol packages). As the Microsoft.DotNet.Build.Tasks.Packaging package won't be maintained by dotnet/runtime any longer, we should get the remaining consumers off it in favor of using the shipping tools (NuGet) instead.

This issue tracks getting repos off the deprecated package and removing it:

• dotnet/runtime mono subset
• dotnet/runtime coreclr subset
• dotnet/runtime installer subset
• dotnet/emsdk
• dotnet/icu
• dotnet/llvm-project
• dotnet/deployment-tools

cc @Anipik @ericstj @akoeplinger (emsdk, icu, llvm-project & mono) @NikolaMilosavljevic (deployment-tools), @markwilkie just FYI

[MattGal]

[Async Triage]: #6811 ?

[markwilkie]

Adding to our partners tracking epic.