Shorten the ClusterInfoVoteListener leader lookahead window

The ClusterInfoVoteListener is responsible for forwarding votes to
BankingStage. The service only forwards votes when the node will be
leader soon, and it determines this by checking the PohRecorder.

As currently written, the service will begin forwarding when the node
will be leader in slot_hashes::MAX_ENTRIES * 3 slots. This comes out to
512 * 3 = 1536 slots. However, any transaction with a blockhash exeeding
MAX_PROCESSING_AGE (150) non-skipped slots is expired and invalid.

Thus, there is no point in sending votes to BankingStage until we are
within MAX_PROCESSING_AGE (150) slots of our leader window. So, shorten
the lookead window down to MAX_PROCESSING_AGE slots.

core/src/cluster_info_vote_listener.rs

@@ -30,11 +30,10 @@ use {
         epoch_stakes::EpochStakes, vote_sender_types::ReplayVoteReceiver,
     },
     solana_sdk::{
-        clock::{Slot, DEFAULT_MS_PER_SLOT, DEFAULT_TICKS_PER_SLOT},
+        clock::{Slot, DEFAULT_MS_PER_SLOT, DEFAULT_TICKS_PER_SLOT, MAX_PROCESSING_AGE},
         hash::Hash,
         pubkey::Pubkey,
         signature::Signature,
-        slot_hashes,
         timing::AtomicInterval,
         transaction::Transaction,
     },
@@ -392,7 +391,7 @@ impl ClusterInfoVoteListener {
             let would_be_leader = poh_recorder
                 .read()
                 .unwrap()
-                .would_be_leader(3 * slot_hashes::MAX_ENTRIES as u64 * DEFAULT_TICKS_PER_SLOT);
+                .would_be_leader(MAX_PROCESSING_AGE as u64 * DEFAULT_TICKS_PER_SLOT);
 
             if let Err(e) = verified_vote_packets.receive_and_process_vote_packets(
                 &verified_vote_label_packets_receiver,