Refactor data column reconstruction and avoid blocking processing (#6403)

* Move reconstruction logic out of `overflow_lru_cache` to simplify the code and avoids having to pass `DataColumnsToPublish` around and blocking other processing.

* Publish reconstructed cells before recomputing head. Remove duplicate functions.

* Merge branch 'unstable' into non-blocking-reconstruction

* Merge branch 'unstable' into non-blocking-reconstruction

# Conflicts:
#	beacon_node/beacon_chain/src/beacon_chain.rs
#	beacon_node/beacon_chain/src/data_availability_checker.rs
#	beacon_node/beacon_chain/src/data_availability_checker/overflow_lru_cache.rs
#	beacon_node/network/src/network_beacon_processor/sync_methods.rs

* Spawn a blocking task for reconstruction.

* Merge branch 'unstable' into non-blocking-reconstruction

# Conflicts:
#	beacon_node/network/src/network_beacon_processor/mod.rs

* Fix fmt

* Merge branch 'unstable' into non-blocking-reconstruction

# Conflicts:
#	beacon_node/beacon_chain/src/data_availability_checker/overflow_lru_cache.rs

* Fix race condition by making check and mutation atomic as suggested by Lion. Also added error handling to reconstruction failure.

* Add reconstruction reason metric and more debug logging to da checker.

* Add comment and logging.

* Rename `NotRequired` to `NotStarted`.

* Remove extra character added.

beacon_node/beacon_chain/src/builder.rs

@@ -984,6 +984,7 @@ where
                     store,
                     self.import_all_data_columns,
                     self.spec,
+                    log.new(o!("service" => "data_availability_checker")),
                 )
                 .map_err(|e| format!("Error initializing DataAvailabilityChecker: {:?}", e))?,
             ),