fix(sol): minor issues and code quality

[kiseln]

max_used_nonce not updating

When finalizing a transfer, max_used_nonce value must be updated in the config account. This is needed to properly calculate rent required for nonce accounts. This wasn't happening because the config instance in the common WormholeCPI struct is not marked mutable.

Fix

I decided to keep the config in the shared struct immutable. It's used in 6 different methods and only two (finalize_transfer and finalize_transfer_sol) need to mutate the config. Instead, I added a separate mutable config instance, same way it is already done for finalize_transfer_sol

Wrong account passed to metaplex instruction

The program id is internally ovewritten with the correct instruction, so the code was working as intended. Still rather fix this.

Remove unwraps

Minor code quality cleanup

Remove unsafe code

unsafe block in used_nonces.rs was unnecessary

[karim-en]

let's cover these changes by test using LiteSVM or Mollusk
https://www.anchor-lang.com/docs/testing

[karim-en]

@kiseln