Create final version flow design.

[mmitche]

Create a design for how version flow should work in the VMR in source-only and normal build scenarios. See #4048 for initial thoughts. It may be that the temporary solution (different graph in MSFT build mode) suffices. I think we should wait and see what the experience is there before working on a design.

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]

The design ended up not need much design. Closing.