Rename/Split VerifiedCredentialV2 to be indicative of verification state

[insipx]

Is your feature request related to a problem?

Initial context: https://github.com/xmtp/libxmtp/pull/689/files#r1594773059

Describe the solution to the problem

VerifiedKeyPackageV2 (Key Package verification for InboxId KeyPackages) are not truly verified client-side, since client has not checked for the existence of an InboxID. The way VerifiedKeyPackageV2 exists today is still useful from the standpoint of MLS Validation Service/XmtpNodeGo.

Describe the uses cases for the feature

Split VerifiedKeyPackageV2 into ParsedKeyPackage and VerifiedKeyPackage. ParsedKeyPackage would be largely similar to VerifiedKeyPackageV2 as it is today, VerifiedKeyPackage would do the actual verification checks. ParsedKeyPackage can be made into a VerifiedKeyPackage via a TryFrom Implementation.

Additional details

No response