add linked-list capability to accounts
change accounts from a linked list to a VecDeque
add checkpoint and rollback for lastids
add subscriber notifications for rollbacks
checkpoint transaction count, too
* Move finality computation into a service run from the banking stage, ComputeLeaderFinalityService
* Change last ids nth to tick height, remove separate tick height from bank
* Add PoH height to process_ledger()
* Moved broadcast_stage Leader Scheduling logic to use Poh height instead of entry_height
* Moved LeaderScheduler logic to PoH in ReplicateStage
* Fix Leader scheduling tests to use PoH instead of entry height
* Change is_leader detection in repair() to use PoH instead of entry height
* Add tests to LeaderScheduler for new functionality
* fix Entry::new and genesis block PoH counts
* Moved LeaderScheduler to PoH ticks
* Cleanup to resolve PR comments
Generate tick entry ids and only register ticks as the last_id expected by the bank. Since the bank is MT, the in-flight pipeline of transactions cannot be close to the end of the queue or there is a high possibility that a starved thread will encode an expired last_id into the ledger. The banking_stage therefore uses a shorter age limit for encoded last_ids then the validators.
Bench client doesn't send transactions that are older then 30 seconds.