Move blocktree_processor to solana_ledger (#6460)

* Drop core::result dependency in bank_forks

* Move blocktree_processor into solana_ledger

core/src/consensus.rs

@@ -1,4 +1,4 @@
-use crate::bank_forks::BankForks;
+use solana_ledger::bank_forks::BankForks;
 use solana_metrics::datapoint_debug;
 use solana_runtime::bank::Bank;
 use solana_sdk::account::Account;