Optimize account copies and use RefCell to handle duplicate accounts in BPF programs (#7958)

programs/bpf/rust/external_spend/src/lib.rs

@@ -8,7 +8,7 @@ fn process_instruction(_program_id: &Pubkey, accounts: &mut [AccountInfo], _data
     // account 0 is the mint and not owned by this program, any debit of its lamports
     // should result in a failed program execution.  Test to ensure that this debit
     // is seen by the runtime and fails as expected
-    *accounts[0].lamports -= 1;
+    *accounts[0].m.borrow_mut().lamports -= 1;
 
     SUCCESS
 }