CPI Account Reuse (#19762)

* Removes two account copy steps from InstructionProcessor::native_invoke().

* Moves gathering of keyed_accounts, caller_write_privileges and program_indices into InstructionProcessor::create_message().

* Explicitly routes the serialized account lengths to enable sharing of existing account structures.

* Recycles existing account structs in CPI syscall.

rbpf-cli/src/main.rs

@@ -170,7 +170,8 @@ native machine code before execting it in the virtual machine.",
             }
             let lid = bpf_loader::id();
             let pid = Pubkey::new(&[0u8; 32]);
-            let mut bytes = serialize_parameters(&lid, &pid, &accounts, &input.insndata).unwrap();
+            let (mut bytes, _account_lenghts) =
+                serialize_parameters(&lid, &pid, &accounts, &input.insndata).unwrap();
             Vec::from(bytes.as_slice_mut())
         }
     };