Remove CountUnrealized (#4357)

## Issue Addressed

Closes #4332

## Proposed Changes

Remove the `CountUnrealized` type, defaulting unrealized justification to _on_. This fixes the #4332 issue by ensuring that importing the same block to fork choice always results in the same outcome.

Finalized sync speed may be slightly impacted by this change, but that is deemed an acceptable trade-off until the optimisation from #4118 is implemented.

TODO:

- [x] Also check that the block isn't a duplicate before importing

testing/ef_tests/src/cases/fork_choice.rs

@@ -7,7 +7,7 @@ use beacon_chain::{
         obtain_indexed_attestation_and_committees_per_slot, VerifiedAttestation,
     },
     test_utils::{BeaconChainHarness, EphemeralHarnessType},
-    BeaconChainTypes, CachedHead, CountUnrealized, NotifyExecutionLayer,
+    BeaconChainTypes, CachedHead, NotifyExecutionLayer,
 };
 use execution_layer::{json_structures::JsonPayloadStatusV1Status, PayloadStatusV1};
 use serde::Deserialize;
@@ -381,7 +381,6 @@ impl<E: EthSpec> Tester<E> {
         let result = self.block_on_dangerous(self.harness.chain.process_block(
             block_root,
             block.clone(),
-            CountUnrealized::True,
             NotifyExecutionLayer::Yes,
         ))?;
         if result.is_ok() != valid {
@@ -441,7 +440,6 @@ impl<E: EthSpec> Tester<E> {
                         &state,
                         PayloadVerificationStatus::Irrelevant,
                         &self.harness.chain.spec,
-                        CountUnrealized::True,
                     );
 
                 if result.is_ok() {