Keyring trace flag VERIFIED_ENCRYPTION_CONTEXT

[lavaleri]

C implementation adds this flag to during raw AES onEncrypt, however this wasn't the intention. JS is coming out soon and we need to decide what the definition of this flag must be (and update that definition in the spec), and whether it needs to be ripped out of the C implementation.

Based on team decision, we will keep the current wording for the VERIFIED_ENCRYPTION_CONTEXT and SIGNED_ENCRYPTION_CONTEXT flags. However, we need to fix the raw AES keyring spec such that it now uses these flags on onEncrypt and onDecrypt.