Add BankClient to minimize copypasta

runtime/src/bank_client.rs

@@ -0,0 +1,19 @@
+use crate::bank::Bank;
+use solana_sdk::signature::Keypair;
+use solana_sdk::transaction::{Transaction, TransactionError};
+
+pub struct BankClient<'a> {
+    bank: &'a Bank,
+    keypair: Keypair,
+}
+
+impl<'a> BankClient<'a> {
+    pub fn new(bank: &'a Bank, keypair: Keypair) -> Self {
+        Self { bank, keypair }
+    }
+
+    pub fn process_transaction(&self, tx: &mut Transaction) -> Result<(), TransactionError> {
+        tx.sign(&[&self.keypair], self.bank.last_blockhash());
+        self.bank.process_transaction(tx)
+    }
+}

runtime/src/lib.rs

@@ -1,6 +1,7 @@
 mod accounts;
 pub mod append_vec;
 pub mod bank;
+pub mod bank_client;
 mod blockhash_queue;
 pub mod bloom;
 pub mod loader_utils;