chore: Remove unused Directive::Log

[Ethan-000]

Description

Problem*

noir-lang/noir#2358 (comment)

Summary*

Additional Context

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[TomAFrench]

This breaks the serialization of Circuit. I'd like to perform all of these removals in one go to avoid the need for updating barretenberg multiple times.

[Ethan-000]

i tried to updated serialization in barretenberg in this pr

let me know if theres other parts of the code that need to be changed