Add command to validate notice

[gligneul]

📚 Context

Validating notices and executing vouchers are central steps in our rollups solution.
We need a command to verify that these steps are working as expected.
We can start with notices because they do not have a specific format to be executed; instead, they just need valid proof to be validated.

✔️ Solution

• Add auxiliary function to ethutil package.
• Add command to validate notice.