Store execution block hash in fork choice (#2643)

* - Update the fork choice `ProtoNode` to include `is_merge_complete`
- Add database migration for the persisted fork choice

* update tests

* Small cleanup

* lints

* store execution block hash in fork choice rather than bool

consensus/proto_array/src/fork_choice_test_definition.rs

@@ -57,6 +57,7 @@ impl ForkChoiceTestDefinition {
     pub fn run(self) {
         let junk_shuffling_id =
             AttestationShufflingId::from_components(Epoch::new(0), Hash256::zero());
+        let execution_block_hash = Hash256::zero();
         let mut fork_choice = ProtoArrayForkChoice::new(
             self.finalized_block_slot,
             Hash256::zero(),
@@ -65,6 +66,7 @@ impl ForkChoiceTestDefinition {
             self.finalized_root,
             junk_shuffling_id.clone(),
             junk_shuffling_id,
+            execution_block_hash,
         )
         .expect("should create fork choice struct");
 
@@ -139,6 +141,7 @@ impl ForkChoiceTestDefinition {
                         ),
                         justified_epoch,
                         finalized_epoch,
+                        execution_block_hash,
                     };
                     fork_choice.process_block(block).unwrap_or_else(|e| {
                         panic!(