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

accounts-bench/src/main.rs

@@ -6,6 +6,7 @@ use rayon::prelude::*;
 use solana_measure::measure::Measure;
 use solana_runtime::{
     accounts::{create_test_accounts, update_accounts_bench, Accounts},
+    accounts_db::AccountShrinkThreshold,
     accounts_index::AccountSecondaryIndexes,
     ancestors::Ancestors,
 };
@@ -64,6 +65,7 @@ fn main() {
         &ClusterType::Testnet,
         AccountSecondaryIndexes::default(),
         false,
+        AccountShrinkThreshold::default(),
     );
     println!("Creating {} accounts", num_accounts);
     let mut create_time = Measure::start("create accounts");