Make account shrink configurable #17544 (#17778)

1. Added both options for measuring space usage using total accounts usage and for individual store shrink ratio using an enum. Validator CLI options: --accounts-shrink-optimize-total-space and --accounts-shrink-ratio
2. Added code for selecting candidates based on total usage in a separate function select_candidates_by_total_usage
3. Added unit tests for the new functions added
4. The default implementations is kept at 0.8 shrink ratio with --accounts-shrink-optimize-total-space set to true

Fixes #17544

local-cluster/src/validator_configs.rs

@@ -56,6 +56,7 @@ pub fn safe_clone_config(config: &ValidatorConfig) -> ValidatorConfig {
         validator_exit: Arc::new(RwLock::new(Exit::default())),
         poh_hashes_per_batch: config.poh_hashes_per_batch,
         no_wait_for_vote_to_start_leader: config.no_wait_for_vote_to_start_leader,
+        accounts_shrink_ratio: config.accounts_shrink_ratio,
     }
 }