Tracking: Add check for build SHA to darc publishing

During the validation of .NET 7 preview 5 (around June 7th, 2022), we realized that an unserviceable roslyn SHA had been inserted into the SDK/installer.
Specifically, SDK version: `7.0.100-preview.5.22305.3` contained roslyn version: `4.3.0-3.22304.2 (fb73a123)`, but the `fb73a1231560b6238ae7d8215e62bfc6e1312159` SHA is an unofficial SHA (resulting from a local merge on a build machine). It does not exist in any git repo.
This was the result of a bad Maestro channel configuration.

A proposal to address this systematically was to add a validation that arcade would only push "official" SHAs.
But from discussion with @mmitche, there are concerns that such a check would add significant complexity (add git dependency) and might not be worthwhile.

This seems a reasonable concern, so I'm creating an issue for tracking purpose where we can record such incidents. The issue can be closed/punted for now. If this happens a few times and across different repos, we may reconsider implementing a centralized check.

FYI @JoeRobich @jaredpar