Better partial diagnosics (#9436)

Small collection of improved diagnostics for partials.


  - In the peer info struct (exposing peer data via `/lighthouse/peers`), add a new field to indicate on which subnets the peer supports partials.
- Fix the description of several metrics.
- Downgrade some noisy logging when sending partials to trace, and downgrade one warning that should not worry the user.


Co-Authored-By: Daniel Knopik <daniel@dknopik.de>

beacon_node/network/src/network_beacon_processor/gossip_methods.rs

@@ -1161,7 +1161,7 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
                 metrics::inc_counter(
                     &metrics::BEACON_PROCESSOR_GOSSIP_PARTIAL_DATA_COLUMN_SIDECAR_MISSING_HEADER_TOTAL,
                 );
-                warn!(
+                debug!(
                     error = ?err,
                     %block_root,
                     %index,