Etherlink/Kernel: A blueprint can have etherlink transactions but also tezos transactions

What

Introduce tezos transactions in the kernel blueprints to prepare tezlink. It also introduce a new module transaction that is extracted from inbox.rs.

This new module transaction will be able to handle ethereum transaction (delayed, deposit, basic, fa_deposit) or tezos transaction.

Why

For tezlink support, we are starting to make a tezlink chain with empty tezos block so wejust need an enum to represent the transactions but no need to have a real vector.

In the future etherlink and tezlink could share aspect like delayed, deposit, basic, fa_deposit.

A transaction could be a delayed transaction of ethereum or tezos transaction.

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR