LoPri: Callers for UKM hooks that return MessageResult

[virgil-serbanuta]

No description provided.

[virgil-serbanuta]

Needs #123 and #137

It's not clear what we need to do when the returned message contains an error - do we throw an error for the current call automatically, or do we allow the Rust code to decide?

Otherwise, it should be handled in the same way as the hooks that return Bytes or Int256 (see #133) - evaluate to messageResultStructFromKMessageResult.