Support Source Build releases with VMR-lite

[premun]

Context

We expect there will be infrastructure and tooling work needed throughout the .NET 8 timeframe so that the VMR-lite supports the efforts of the Source Build team when delivering the Source Build to our .NET partners.

We also expect some unification efforts with regards to the SB release pipelines for .NET 6.0/7.0 and newly 8.0.

Business goal

.NET 8 previews, RCs and RTM releases of Source Build happen from VMR-lite. The VMR also serves as a vehicle for speeding up the work and maintenance of Source Build.

[tkapin]

This is still in progress, container for various assorted SB / VMR issues.