Refactor slot status notification to decouple from accounts notifications (#21308)

Problem

Slot status can be used of in other scenarios in addition to account information such as transactions, blocks. The current implementation is too tightly coupled.

Summary of Changes

Decouple the slot status notification from accounts notification. Created a new slot status notification module.

accountsdb-plugin-postgres/src/accounts_selector.rs

@@ -48,6 +48,11 @@ impl AccountsSelector {
     pub fn is_account_selected(&self, account: &[u8], owner: &[u8]) -> bool {
         self.select_all_accounts || self.accounts.contains(account) || self.owners.contains(owner)
     }
+
+    /// Check if any account is of interested at all
+    pub fn is_enabled(&self) -> bool {
+        self.select_all_accounts || !self.accounts.is_empty() || !self.owners.is_empty()
+    }
 }
 
 #[cfg(test)]