[VMR] Windows Vertical Build PoC

[mmitche]

Objective

As part of https://github.com/dotnet/arcade/blob/main/Documentation/UnifiedBuild/UB-Roadmap.md, we want to produce vertical build(s) for Windows in order to flush out any problematic areas and continue to shape our VMR approach for .NET 9.

Outcomes

• The PoC can produce the customer facing artifacts that .NET produces in its current official build (or we know we can produce such an artifact by completing a specified set of work).
• Issues are filed providing a clear path between the PoC and productization of the VMR vertical.
• A rolling CI leg is added to the VMR to identify breaks in the PoC

Work Items

• Produce windows-x64 vertical
• Produce windows-arm64 vertical
• Produce windows-arm32 vertical
• [VMR] Introduce WindowsDesktop to the VMR #3681

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[mmitche]

@ViktorHofer I am calling the PoC basically done. It is checked in, largely upstreamed, and we are working on actually productizing things at this point.