Improve Notary Service API to simplify multi-signature transaction signing

[End-rey]

Is your feature request related to a problem? Please describe.

Currently, signing transactions in the notary service requires manual manipulation of invocation scripts. This includes removing existing invocation script from the transaction that was received from the notary pool, and ensuring the correct actor is used to match the transaction's original signers. This process is cumbersome, error-prone, and counterintuitive, especially when the goal is simply to append a signature to an existing transaction.

Describe the solution you'd like

Just use GetRawNotaryTransactionVerbose + Sign (or any other method that would make it easier to add a signature obtained from the notary pool) and everything works.

Describe alternatives you've considered

Current Manual Process:

1. Retrieve the transaction using GetRawNotaryTransactionVerbose.
2. Manually strip all existing invocation scripts.
3. Use Sign with a properly configured actor.

This works but is not user-friendly and can lead to confusion or errors, as noted during debugging.