Add accounts-bench, a benchmark to test the accounts store speed (#8866)

runtime/src/accounts.rs

@@ -12,6 +12,7 @@ use crate::{
     transaction_utils::OrderedIterator,
 };
 use log::*;
+use rand::{thread_rng, Rng};
 use rayon::slice::ParallelSliceMut;
 use solana_sdk::{
     account::Account,
@@ -658,6 +659,14 @@ pub fn create_test_accounts(
     }
 }
 
+pub fn update_accounts(accounts: &Accounts, pubkeys: &[Pubkey], slot: u64) {
+    for pubkey in pubkeys {
+        let amount = thread_rng().gen_range(0, 10);
+        let account = Account::new(amount, 0, &Account::default().owner);
+        accounts.store_slow(slot, &pubkey, &account);
+    }
+}
+
 #[cfg(test)]
 mod tests {
     // TODO: all the bank tests are bank specific, issue: 2194