Range sync: fetch data columns via custody-by-root (#9496)

- Generalize the custody-by-root request to accept a `Vec<Hash256>` of block roots so a whole batch is fetched in one request; `DataColumnsByRootRequestParams { block_roots, indices }` completes at `block_roots.len() * indices.len()`.
- `custody_lookup_request` takes `block_roots: &[Hash256]` + `block_epoch`; `cached_data_column_indexes` takes `block_epoch`.
- `block_sidecar_coupling.rs`: couple a batch's blocks with the columns returned by the single custody-by-root request; drop the per-column request map and retry/faulty-peer machinery.
- Remove the now-unused columns-by-range range-sync path and the serialize-downloads gate.


Co-Authored-By: dapplion <35266934+dapplion@users.noreply.github.com>

beacon_node/lighthouse_network/tests/rpc_tests.rs

@@ -9,7 +9,8 @@ use libp2p::PeerId;
 use lighthouse_network::rpc::{RequestType, methods::*};
 use lighthouse_network::service::api_types::{
     AppRequestId, BlobsByRangeRequestId, BlocksByRangeRequestId, ComponentsByRangeRequestId,
-    DataColumnsByRangeRequestId, DataColumnsByRangeRequester, RangeRequestId, SyncRequestId,
+    CustodyBackFillBatchRequestId, CustodyBackfillBatchId, DataColumnsByRangeRequestId,
+    DataColumnsByRangeRequester, RangeRequestId, SyncRequestId,
 };
 use lighthouse_network::{NetworkEvent, ReportSource, Response};
 use ssz::Encode;
@@ -1828,12 +1829,12 @@ fn test_request_too_large_data_columns_by_range() {
         AppRequestId::Sync(SyncRequestId::DataColumnsByRange(
             DataColumnsByRangeRequestId {
                 id: 1,
-                parent_request_id: DataColumnsByRangeRequester::ComponentsByRange(
-                    ComponentsByRangeRequestId {
+                parent_request_id: DataColumnsByRangeRequester::CustodyBackfillSync(
+                    CustodyBackFillBatchRequestId {
                         id: 1,
-                        requester: RangeRequestId::RangeSync {
-                            chain_id: 1,
-                            batch_id: Epoch::new(1),
+                        batch_id: CustodyBackfillBatchId {
+                            epoch: Epoch::new(1),
+                            run_id: 1,
                         },
                     },
                 ),