Accountsdb plugin postgres -- bulk insertion at startup (#20763)

Use bulk insertion to Postgres at startup to reduce time taken for initial snapshot restore for postgres plugin. Avoid duplicate writes of accounts at startup. Doing account plugin notification and indexing in parallel.

Improved error handling for postgres plugin to show the real db issues for debug purpose
Added more metrics for postgres plugin.
Refactored plugin centric code out to a sub module from accounts_db and added unit tests

accountsdb-plugin-interface/src/accountsdb_plugin_interface.rs

@@ -25,19 +25,19 @@ pub enum ReplicaAccountInfoVersions<'a> {
 
 #[derive(Error, Debug)]
 pub enum AccountsDbPluginError {
-    #[error("Error opening config file.")]
+    #[error("Error opening config file. Error detail: ({0}).")]
     ConfigFileOpenError(#[from] io::Error),
 
-    #[error("Error reading config file.")]
+    #[error("Error reading config file. Error message: ({msg})")]
     ConfigFileReadError { msg: String },
 
-    #[error("Error updating account.")]
+    #[error("Error updating account. Error message: ({msg})")]
     AccountsUpdateError { msg: String },
 
-    #[error("Error updating slot status.")]
+    #[error("Error updating slot status. Error message: ({msg})")]
     SlotStatusUpdateError { msg: String },
 
-    #[error("Plugin-defined custom error.")]
+    #[error("Plugin-defined custom error. Error message: ({0})")]
     Custom(Box<dyn error::Error + Send + Sync>),
 }
 
@@ -78,7 +78,15 @@ pub trait AccountsDbPlugin: Any + Send + Sync + std::fmt::Debug {
     fn on_unload(&mut self) {}
 
     /// Called when an account is updated at a slot.
-    fn update_account(&mut self, account: ReplicaAccountInfoVersions, slot: u64) -> Result<()>;
+    fn update_account(
+        &mut self,
+        account: ReplicaAccountInfoVersions,
+        slot: u64,
+        is_startup: bool,
+    ) -> Result<()>;
+
+    /// Called when all accounts are notified of during startup.
+    fn notify_end_of_startup(&mut self) -> Result<()>;
 
     /// Called when a slot status is updated
     fn update_slot_status(