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/fork_choice/tests/tests.rs

@@ -104,16 +104,6 @@ impl ForkChoiceTest {
         self
     }
 
-    /// Assert the epochs match.
-    pub fn assert_best_justified_epoch(self, epoch: u64) -> Self {
-        assert_eq!(
-            self.get(|fc_store| fc_store.best_justified_checkpoint().epoch),
-            Epoch::new(epoch),
-            "best_justified_epoch"
-        );
-        self
-    }
-
     /// Assert the given slot is greater than the head slot.
     pub fn assert_finalized_epoch_is_less_than(self, epoch: Epoch) -> Self {
         assert!(self.harness.finalized_checkpoint().epoch < epoch);
@@ -151,7 +141,7 @@ impl ForkChoiceTest {
             .chain
             .canonical_head
             .fork_choice_write_lock()
-            .update_time(self.harness.chain.slot().unwrap(), &self.harness.spec)
+            .update_time(self.harness.chain.slot().unwrap())
             .unwrap();
         func(
             self.harness
@@ -241,6 +231,11 @@ impl ForkChoiceTest {
     ///
     /// If the chain is presently in an unsafe period, transition through it and the following safe
     /// period.
+    ///
+    /// Note: the `SAFE_SLOTS_TO_UPDATE_JUSTIFIED` variable has been removed
+    /// from the fork choice spec in Q1 2023. We're still leaving references to
+    /// it in our tests because (a) it's easier and (b) it allows us to easily
+    /// test for the absence of that parameter.
     pub fn move_to_next_unsafe_period(self) -> Self {
         self.move_inside_safe_to_update()
             .move_outside_safe_to_update()
@@ -534,7 +529,6 @@ async fn justified_checkpoint_updates_with_descendent_outside_safe_slots() {
         .unwrap()
         .move_outside_safe_to_update()
         .assert_justified_epoch(2)
-        .assert_best_justified_epoch(2)
         .apply_blocks(1)
         .await
         .assert_justified_epoch(3);
@@ -551,11 +545,9 @@ async fn justified_checkpoint_updates_first_justification_outside_safe_to_update
         .unwrap()
         .move_to_next_unsafe_period()
         .assert_justified_epoch(0)
-        .assert_best_justified_epoch(0)
         .apply_blocks(1)
         .await
-        .assert_justified_epoch(2)
-        .assert_best_justified_epoch(2);
+        .assert_justified_epoch(2);
 }
 
 /// - The new justified checkpoint **does not** descend from the current.
@@ -583,8 +575,7 @@ async fn justified_checkpoint_updates_with_non_descendent_inside_safe_slots_with
                 .unwrap();
         })
         .await
-        .assert_justified_epoch(3)
-        .assert_best_justified_epoch(3);
+        .assert_justified_epoch(3);
 }
 
 /// - The new justified checkpoint **does not** descend from the current.
@@ -612,8 +603,9 @@ async fn justified_checkpoint_updates_with_non_descendent_outside_safe_slots_wit
                 .unwrap();
         })
         .await
-        .assert_justified_epoch(2)
-        .assert_best_justified_epoch(3);
+        // Now that `SAFE_SLOTS_TO_UPDATE_JUSTIFIED` has been removed, the new
+        // block should have updated the justified checkpoint.
+        .assert_justified_epoch(3);
 }
 
 /// - The new justified checkpoint **does not** descend from the current.
@@ -641,8 +633,7 @@ async fn justified_checkpoint_updates_with_non_descendent_outside_safe_slots_wit
                 .unwrap();
         })
         .await
-        .assert_justified_epoch(3)
-        .assert_best_justified_epoch(3);
+        .assert_justified_epoch(3);
 }
 
 /// Check that the balances are obtained correctly.