NuGet feed non-determinism should be accounted for in Arcade source build

[mthalman]

The changes in dotnet/installer#19114 addressed NuGet's package restore non-determinism as described in #4206 via the use of package source mappings. That same approach is also needed for Arcade source build (aka ArPow) because the source build leg of product repos can also have multiple feeds listed in their NuGet.config files. With this non-determinism, it is possible that a package could be retrieved from an online feed rather than the source built cache feed. That would lead to prebuilts.

[MichaelSimons]

[Triage] This will likely be a problem once arcade updates the SDK to a newer version with the NuGet change.

[MichaelSimons]

[Triage] The speculation is that this might not break at the repo level because there is only one local package feed whereas in the product source build there were multiples.

@NikolaMilosavljevic - this is an issue we feel would be good to proactively address before it becomes a blocking issue.