Enforce Permissible Binary Source Policy

[MichaelSimons]

PR validation should enforce the Permissible Source Policy in regard to binaries. What this means concretely is we scan for binaries in PR validation and fail the build if non-permissible binaries are found.

When should this be enabled? If this is enabled now, it will introduce yet another reason why the sdk->installer dependency flow can break. This may not be in our best interest. This should be enabled for sure when the repo dependency flow is switched to go directly into the VMR. Would it make sense to enable sooner, e.g. once the sdk->installer repos are merged?

[MichaelSimons]

[Triage] This should no be done until after the flat flow is implemented.