Realized unrealized experimentation (#3322)

## Issue Addressed

Add a flag that optionally enables unrealized vote tracking.  Would like to test out on testnets and benchmark differences in methods of vote tracking. This PR includes a DB schema upgrade to enable to new vote tracking style.


Co-authored-by: realbigsean <sean@sigmaprime.io>
Co-authored-by: Paul Hauner <paul@paulhauner.com>
Co-authored-by: sean <seananderson33@gmail.com>
Co-authored-by: Mac L <mjladson@pm.me>

beacon_node/beacon_chain/src/fork_revert.rs

@@ -1,5 +1,5 @@
 use crate::{BeaconForkChoiceStore, BeaconSnapshot};
-use fork_choice::{ForkChoice, PayloadVerificationStatus};
+use fork_choice::{CountUnrealized, ForkChoice, PayloadVerificationStatus};
 use itertools::process_results;
 use slog::{info, warn, Logger};
 use state_processing::state_advance::complete_state_advance;
@@ -99,6 +99,7 @@ pub fn reset_fork_choice_to_finalization<E: EthSpec, Hot: ItemStore<E>, Cold: It
     store: Arc<HotColdDB<E, Hot, Cold>>,
     current_slot: Option<Slot>,
     spec: &ChainSpec,
+    count_unrealized_config: CountUnrealized,
 ) -> Result<ForkChoice<BeaconForkChoiceStore<E, Hot, Cold>, E>, String> {
     // Fetch finalized block.
     let finalized_checkpoint = head_state.finalized_checkpoint();
@@ -163,7 +164,8 @@ pub fn reset_fork_choice_to_finalization<E: EthSpec, Hot: ItemStore<E>, Cold: It
         .map_err(|e| format!("Error loading blocks to replay for fork choice: {:?}", e))?;
 
     let mut state = finalized_snapshot.beacon_state;
-    for block in blocks {
+    let blocks_len = blocks.len();
+    for (i, block) in blocks.into_iter().enumerate() {
         complete_state_advance(&mut state, None, block.slot(), spec)
             .map_err(|e| format!("State advance failed: {:?}", e))?;
 
@@ -183,6 +185,15 @@ pub fn reset_fork_choice_to_finalization<E: EthSpec, Hot: ItemStore<E>, Cold: It
         // This scenario is so rare that it seems OK to double-verify some blocks.
         let payload_verification_status = PayloadVerificationStatus::Optimistic;
 
+        // Because we are replaying a single chain of blocks, we only need to calculate unrealized
+        // justification for the last block in the chain.
+        let is_last_block = i + 1 == blocks_len;
+        let count_unrealized = if is_last_block {
+            count_unrealized_config
+        } else {
+            CountUnrealized::False
+        };
+
         fork_choice
             .on_block(
                 block.slot(),
@@ -193,6 +204,7 @@ pub fn reset_fork_choice_to_finalization<E: EthSpec, Hot: ItemStore<E>, Cold: It
                 &state,
                 payload_verification_status,
                 spec,
+                count_unrealized,
             )
             .map_err(|e| format!("Error applying replayed block to fork choice: {:?}", e))?;
     }