Fork choice modifications and cleanup (#3962)

## Issue Addressed

NA

## Proposed Changes

- Implements https://github.com/ethereum/consensus-specs/pull/3290/
- Bumps `ef-tests` to [v1.3.0-rc.4](https://github.com/ethereum/consensus-spec-tests/releases/tag/v1.3.0-rc.4).

The `CountRealizedFull` concept has been removed and the `--count-unrealized-full` and `--count-unrealized` BN flags now do nothing but log a `WARN` when used.

## Database Migration Debt

This PR removes the `best_justified_checkpoint` from fork choice. This field is persisted on-disk and the correct way to go about this would be to make a DB migration to remove the field. However, in this PR I've simply stubbed out the value with a junk value. I've taken this approach because if we're going to do a DB migration I'd love to remove the `Option`s around the justified and finalized checkpoints on `ProtoNode` whilst we're at it. Those options were added in #2822 which was included in Lighthouse v2.1.0. The options were only put there to handle the migration and they've been set to `Some` ever since v2.1.0. There's no reason to keep them as options anymore.

I started adding the DB migration to this branch but I started to feel like I was bloating this rather critical PR with nice-to-haves. I've kept the partially-complete migration [over in my repo](https://github.com/paulhauner/lighthouse/tree/fc-pr-18-migration) so we can pick it up after this PR is merged.

consensus/proto_array/src/proto_array_fork_choice.rs

@@ -1,8 +1,8 @@
 use crate::{
     error::Error,
     proto_array::{
-        calculate_committee_fraction, CountUnrealizedFull, InvalidationOperation, Iter,
-        ProposerBoost, ProtoArray, ProtoNode,
+        calculate_committee_fraction, InvalidationOperation, Iter, ProposerBoost, ProtoArray,
+        ProtoNode,
     },
     ssz_container::SszContainer,
     JustifiedBalances,
@@ -307,7 +307,6 @@ impl ProtoArrayForkChoice {
         current_epoch_shuffling_id: AttestationShufflingId,
         next_epoch_shuffling_id: AttestationShufflingId,
         execution_status: ExecutionStatus,
-        count_unrealized_full: CountUnrealizedFull,
     ) -> Result<Self, String> {
         let mut proto_array = ProtoArray {
             prune_threshold: DEFAULT_PRUNE_THRESHOLD,
@@ -316,7 +315,6 @@ impl ProtoArrayForkChoice {
             nodes: Vec::with_capacity(1),
             indices: HashMap::with_capacity(1),
             previous_proposer_boost: ProposerBoost::default(),
-            count_unrealized_full,
         };
 
         let block = Block {
@@ -780,13 +778,10 @@ impl ProtoArrayForkChoice {
         SszContainer::from(self).as_ssz_bytes()
     }
 
-    pub fn from_bytes(
-        bytes: &[u8],
-        count_unrealized_full: CountUnrealizedFull,
-    ) -> Result<Self, String> {
+    pub fn from_bytes(bytes: &[u8]) -> Result<Self, String> {
         let container = SszContainer::from_ssz_bytes(bytes)
             .map_err(|e| format!("Failed to decode ProtoArrayForkChoice: {:?}", e))?;
-        (container, count_unrealized_full)
+        container
             .try_into()
             .map_err(|e| format!("Failed to initialize ProtoArrayForkChoice: {e:?}"))
     }
@@ -950,7 +945,6 @@ mod test_compute_deltas {
             junk_shuffling_id.clone(),
             junk_shuffling_id.clone(),
             execution_status,
-            CountUnrealizedFull::default(),
         )
         .unwrap();
 
@@ -1076,7 +1070,6 @@ mod test_compute_deltas {
             junk_shuffling_id.clone(),
             junk_shuffling_id.clone(),
             execution_status,
-            CountUnrealizedFull::default(),
         )
         .unwrap();