Improve get_custody_columns validation, caching and error handling (#6308)

* Improve `get_custody_columns` validation, caching and error handling.

* Merge branch 'unstable' into get-custody-columns-error-handing

* Fix failing test and add more test.

* Fix failing test and add more test.

* Merge branch 'unstable' into get-custody-columns-error-handing

# Conflicts:
#	beacon_node/lighthouse_network/src/discovery/subnet_predicate.rs
#	beacon_node/lighthouse_network/src/peer_manager/peerdb.rs
#	beacon_node/lighthouse_network/src/peer_manager/peerdb/peer_info.rs
#	beacon_node/lighthouse_network/src/types/globals.rs
#	beacon_node/network/src/service.rs
#	consensus/types/src/data_column_subnet_id.rs

* Add unit test to make sure the default specs won't panic on the `compute_custody_requirement_subnets` function.

* Add condition when calling `compute_custody_subnets_from_metadata` and update logs.

* Validate `csc` when returning from enr. Remove `csc` computation on connection since we get them on metadata anyway.

* Add `peers_per_custody_subnet_count` to track peer csc and supernodes.

* Disconnect peers with invalid metadata and find other peers instead.

* Fix sampling tests.

* Merge branch 'unstable' into get-custody-columns-error-handing

* Merge branch 'unstable' into get-custody-columns-error-handing

testing/ef_tests/src/cases/get_custody_columns.rs

@@ -31,6 +31,7 @@ impl<E: EthSpec> Case for GetCustodyColumns<E> {
             self.custody_subnet_count,
             &spec,
         )
+        .expect("should compute custody columns")
         .collect::<Vec<_>>();
         let expected = &self.result;
         if computed == *expected {