Refactor consensus/types (#7827)

Organize and categorize `consensus/types` into modules based on their relation to key consensus structures/concepts.
This is a precursor to a sensible public interface.

While this refactor is very opinionated, I am open to suggestions on module names, or type groupings if my current ones are inappropriate.


Co-Authored-By: Mac L <mjladson@pm.me>

beacon_node/beacon_chain/src/test_utils.rs

@@ -46,6 +46,7 @@ use rand::seq::SliceRandom;
 use rayon::prelude::*;
 use sensitive_url::SensitiveUrl;
 use slot_clock::{SlotClock, TestingSlotClock};
+use ssz_types::RuntimeVariableList;
 use state_processing::per_block_processing::compute_timestamp_at_slot;
 use state_processing::state_advance::complete_state_advance;
 use std::borrow::Cow;