Use KeyVaultIdentifier everywhere in Key Vault

[heaths]

While working on another issue, I found duplicated logic that the KeyVaultIdentifier struct in .Shared already does. In Secrets, it's ObjectId. Keys has KeyProperties.ParseId, and Certificates has CertificateProperties.ParseId.

The exceptions are more specific to what is wrong, but all throw an ArgumentException already. They also assert the collection, but I think this might largely be irrelevant. At the very least, we should consolidate that logic into KeyVaultIdentifier much like the original struct was which did assert the collection like "secrets" or "keys".