rework defaults and construction of accountsdb, accounts, bank (#19083)

* rework defaults and construction of accountsdb, accounts, bank

* merge issues

runtime/src/accounts.rs

@@ -87,7 +87,7 @@ impl AccountLocks {
 }
 
 /// This structure handles synchronization for db
-#[derive(Default, Debug, AbiExample)]
+#[derive(Debug, AbiExample)]
 pub struct Accounts {
     /// Single global AccountsDb
     pub accounts_db: Arc<AccountsDb>,
@@ -97,6 +97,15 @@ pub struct Accounts {
     pub(crate) account_locks: Mutex<AccountLocks>,
 }
 
+impl Default for Accounts {
+    fn default() -> Self {
+        Self {
+            accounts_db: Arc::new(AccountsDb::default()),
+            account_locks: Mutex::default(),
+        }
+    }
+}
+
 // for the load instructions
 pub type TransactionAccounts = Vec<(Pubkey, AccountSharedData)>;
 pub type TransactionRent = u64;
@@ -117,6 +126,13 @@ pub enum AccountAddressFilter {
 }
 
 impl Accounts {
+    pub fn default_for_tests() -> Self {
+        Self {
+            accounts_db: Arc::new(AccountsDb::default_for_tests()),
+            account_locks: Mutex::default(),
+        }
+    }
+
     pub fn new(
         paths: Vec<PathBuf>,
         cluster_type: &ClusterType,