test: Refactor MiniWallet sign_tx

To make the code less verbose and easier to read.

test/functional/test_framework/wallet.py

@@ -180,12 +180,12 @@ class MiniWallet:
             tx.vin[0].scriptSig = CScript([der_sig + bytes(bytearray([SIGHASH_ALL]))])
             tx.rehash()
         elif self._mode == MiniWalletMode.RAW_OP_TRUE:
-            for i in range(len(tx.vin)):
+            for i in tx.vin:
-                tx.vin[i].scriptSig = CScript([OP_NOP] * 43)  # pad to identical size
+                i.scriptSig = CScript([OP_NOP] * 43)  # pad to identical size
         elif self._mode == MiniWalletMode.ADDRESS_OP_TRUE:
             tx.wit.vtxinwit = [CTxInWitness()] * len(tx.vin)
-            for i in range(len(tx.vin)):
+            for i in tx.wit.vtxinwit:
-                tx.wit.vtxinwit[i].scriptWitness.stack = [CScript([OP_TRUE]), bytes([LEAF_VERSION_TAPSCRIPT]) + self._internal_key]
+                i.scriptWitness.stack = [CScript([OP_TRUE]), bytes([LEAF_VERSION_TAPSCRIPT]) + self._internal_key]
         else:
             assert False