Remove CGC from data_availability checker (#7033)

- Part of https://github.com/sigp/lighthouse/issues/6767

Validator custody makes the CGC and set of sampling columns dynamic. Right now this information is stored twice:
- in the data availability checker
- in the network globals

If that state becomes dynamic we must make sure it is in sync updating it twice, or guarding it behind a mutex. However, I noted that we don't really have to keep the CGC inside the data availability checker. All consumers can actually read it from the network globals, and we can update `make_available` to read the expected count of data columns from the block.

beacon_node/network/src/sync/block_sidecar_coupling.rs

@@ -257,8 +257,14 @@ impl<E: EthSpec> RangeBlockComponentsRequest<E> {
                     ));
                 }
 
-                RpcBlock::new_with_custody_columns(Some(block_root), block, custody_columns, spec)
-                    .map_err(|e| format!("{e:?}"))?
+                RpcBlock::new_with_custody_columns(
+                    Some(block_root),
+                    block,
+                    custody_columns,
+                    expects_custody_columns.len(),
+                    spec,
+                )
+                .map_err(|e| format!("{e:?}"))?
             } else {
                 RpcBlock::new_without_blobs(Some(block_root), block)
             });