Performance: Retransmit Shred

[bw-solana]

Ability to disseminate shreds quickly through turbine is crucial to ensure timely replay and thus minimal skipped slots, even with larger block capacity.

As block capacity grows, number of shreds increase, and worst case delivery can increase.

It has been observed that as number of shreds 5xs (~1.5k to 9k), median turbine block delivery times can increase almost 2x (~400ms to ~700ms).

Making shred processing, verification, and retransmit faster will help here.

• removes intermediate vector allocations in ClusterNodes::get_retransmit_addrs #4146