VMR source-only build should flow repo symbols to intermediates

[NikolaMilosavljevic]

Publishing work in dotnet/installer#18917 has updated the model for propagating repo symbols to VMR source-only build. Symbols archives are published to assets folder (Symbols sub-folder) - utilizing arcade publishing step.

There are several issues with this approach:

• Symbols archives are copied to assets instead of intermediates. These are not customer-facing packages.
• There is an unnecessary compression and extraction step.
• Publishing infra is handling these source-only intermediates packages.

@ViktorHofer suggested the following solution:

• Symbols-related infra should be moved to AfterSourceBuild.proj, outside of publishing infra.
• VMR orchestrator should pass the repo-specific symbols location (in intermediates) to the repo build.
• Repo inner-build should copy the symbols directly, without utilizing the archive, thus saving some build time.