MakeOfficialBuildId= the default for source-only non-official build setup

[ViktorHofer]

Same issue as #4613 but for source-only builds

This needs to wait until we snap for Preview 3 to only apply to Preview 4 and later which is when we start shipping from the VMR.

[MichaelSimons]

[Triage] Some additional changes are needed as a result of making this. The source build release process would need to include the OfficialBuildId info as part of the release. Additionally when doing the final builds, there needs to be a source build CI run with the same OfficialBuildId input in order to produce the artifacts and sdks that get uploaded to blob storage. How would these builds get queued is something that needs to be flushed out.

[MichaelSimons]

Stable versioning would make this UX a lot better for end users as they would not have to specify the OfficialBuildId.