Ensure no signed files skip verification

[ellahathaway]

Not all files that can be validated on .NET Core can be validated on .NET Framework, and vise-versa. See https://github.com/dotnet/arcade/blob/e52018af7f5bab97b0721382d52badfc7edb54f6/src/SignCheck/Microsoft.SignCheck/Verification/SignatureVerificationManager.cs#L91-L117 for the full list.

Due to these differences, we should verify that no signed files skip verification between the Mac, Linux, and Windows verification legs. This work will be more of a sanity check and does not need to go into prod.