Committee as entry point

[MatheusFranco99]

Overview

This PR makes the Committee structure the entry point in the SSV module.

Before, we had both Committee and Validator as distinct entry points. Now, Committee holds Validator objects and redirects messages and duty-start events to the appropriate validator object.

Extra changes

As refactoring, this PR also:

• drops unused attributes of the Validator structure
• refactors the previous ProcessMessage function existent in Committee and Validator to a unique one to avoid duplicated knowledge

Added tests

• Unknown duty type
• Unknown validator for committee
• Message validation: empty data
• Message validation: unknown MsgType

Note

For the test case of a message with MessageID that doesn't belong to either the committee or to a validator, we already had the WrongMessageID test. Thus, we simply aligned the error string.

Closes #451