Resolve architect board feedback for Key Vault

[heaths]

Here are a few things that came up during the archboard review. Note that there is a discussion about whether to expose a LocalCryptographyClient or make it a "mode" of CryptographyClient, but that should only apply to .NET and Java. That is not listed below as prototyping is necessary. But #18575 is tracking that work.

• Add service version for "7.2". Don't bother with "7.2-preview". It won't be supported anyway, most likely, and "7.2" already is supported by both Key Vault and Managed HSM (rather, Managed HSM ignores it).
• Rename EncryptOptions to EncryptParameters.
• Rename DecryptOptions to DecryptParameters.
• AdditionalAuthenticatedData should be a read-only property (no setters).
• KeyVaultKeyIdentifier (as well as for secrets and certificates) should not have "parse" methods, but instead take the URI into the constructor/creator. This pattern will, of course, vary from language to language.
• Make sure all properties on JsonWebKey are settable (came up indirectly, but this should be the case already).
• (.NET) KeyVault*Identifier structs should implement IEquatable<T>.