token client: refactor transfer to use new offchain helper

This PR continues the necessary repairs for addressing #6064 by refactoring the
Token Client's `transfer(..)` function to use the new offchain transfer hook
helpers.

If transfer hook accounts are provided, in either case they're appended to the
instruction like before.

If no transfer hook accounts are provided:
- If decimals are provided, Token2022's offchain helper
  `create_transfer_checked_instruction_with_extra_metas(..)` is used.
- If decimals are not provided, SPL Transfer Hook interface's
  `add_extra_account_metas_for_execute(..)` is used.

In either case where no transfer hook accounts are provided, the new,
non-deprecated helpers are used.

Author: Joe C

token/client/src/token.rs

@@ -913,17 +913,41 @@ where
         let signing_pubkeys = signing_keypairs.pubkeys();
         let multisig_signers = self.get_multisig_signers(authority, &signing_pubkeys);
 
-        let mut instruction = if let Some(decimals) = self.decimals {
-            instruction::transfer_checked(
-                &self.program_id,
-                source,
-                &self.pubkey,
-                destination,
-                authority,
-                &multisig_signers,
-                amount,
-                decimals,
-            )?
+        let fetch_account_data_fn = |address| {
+            self.client
+                .get_account(address)
+                .map_ok(|opt| opt.map(|acc| acc.data))
+        };
+
+        let instruction = if let Some(decimals) = self.decimals {
+            if let Some(transfer_hook_accounts) = &self.transfer_hook_accounts {
+                let mut instruction = instruction::transfer_checked(
+                    &self.program_id,
+                    source,
+                    self.get_address(),
+                    destination,
+                    authority,
+                    &multisig_signers,
+                    amount,
+                    decimals,
+                )?;
+                instruction.accounts.extend(transfer_hook_accounts.clone());
+                instruction
+            } else {
+                offchain::create_transfer_checked_instruction_with_extra_metas(
+                    &self.program_id,
+                    source,
+                    self.get_address(),
+                    destination,
+                    authority,
+                    &multisig_signers,
+                    amount,
+                    decimals,
+                    fetch_account_data_fn,
+                )
+                .await
+                .map_err(|_| TokenError::AccountNotFound)?
+            }
         } else {
             #[allow(deprecated)]
             instruction::transfer(
@@ -935,22 +959,6 @@ where
                 amount,
             )?
         };
-        if let Some(transfer_hook_accounts) = &self.transfer_hook_accounts {
-            instruction.accounts.extend(transfer_hook_accounts.clone());
-        } else {
-            #[allow(deprecated)]
-            offchain::resolve_extra_transfer_account_metas(
-                &mut instruction,
-                |address| {
-                    self.client
-                        .get_account(address)
-                        .map_ok(|opt| opt.map(|acc| acc.data))
-                },
-                self.get_address(),
-            )
-            .await
-            .map_err(|_| TokenError::AccountNotFound)?;
-        };
 
         self.process_ixs(&[instruction], signing_keypairs).await
     }