EVM/Node: add Ethereum's subscription RPCs types and encodings

Context

#7594 (closed)

Part. of %Websockets in EVM node.

Depends of !15566 (merged).

This MR adds the encoding and types for the subscriptions. Specification can be found here.

Next: !15899 (merged).

Manually testing the MR

See !15899 (merged).

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