Add rent estimation rpc (#6109)

* server side new rpc endpoint

* client side rpc

* take data_len as usize

Co-Authored-By: Tyera Eulberg <teulberg@gmail.com>

* add test and documentation

runtime/src/bank.rs

@@ -679,6 +679,12 @@ impl Bank {
         self.blockhash_queue.read().unwrap().last_hash()
     }
 
+    pub fn get_minimum_balance_for_rent_exemption(&self, data_len: usize) -> u64 {
+        self.rent_collector
+            .rent_calculator
+            .minimum_balance(data_len)
+    }
+
     pub fn last_blockhash_with_fee_calculator(&self) -> (Hash, FeeCalculator) {
         let blockhash_queue = self.blockhash_queue.read().unwrap();
         let last_hash = blockhash_queue.last_hash();