Remove deprecated flags in prep for v6.0.0 (#6490)

* Delete previously deprecated flags

* Update CLI docs

* Remove deprecated BN flags

* Use ethereum-package main branch

* Delete env_log/-l

beacon_node/operation_pool/src/lib.rs

@@ -1,5 +1,4 @@
 mod attestation;
-mod attestation_id;
 mod attestation_storage;
 mod attester_slashing;
 mod bls_to_execution_changes;