Merge remote-tracking branch 'origin/unstable' into capella

Fixing the conflicts involved patching up some of the `block_hash` verification,
the rest will be done as part of https://github.com/sigp/lighthouse/issues/3870

beacon_node/beacon_chain/src/chain_config.rs

@@ -65,6 +65,8 @@ pub struct ChainConfig {
     /// Low values are useful for execution engines which don't improve their payload after the
     /// first call, and high values are useful for ensuring the EL is given ample notice.
     pub prepare_payload_lookahead: Duration,
+    /// Use EL-free optimistic sync for the finalized part of the chain.
+    pub optimistic_finalized_sync: bool,
 }
 
 impl Default for ChainConfig {
@@ -89,6 +91,9 @@ impl Default for ChainConfig {
             count_unrealized_full: CountUnrealizedFull::default(),
             checkpoint_sync_url_timeout: 60,
             prepare_payload_lookahead: Duration::from_secs(4),
+            // TODO(capella): disabled until withdrawal verification is implemented
+            // See: https://github.com/sigp/lighthouse/issues/3870
+            optimistic_finalized_sync: false,
         }
     }
 }