Use specific tx formats compatible with sighash algorithms

ZIP 244 is only defined for v5 transactions, so use the TransactionV5
type directly; likewise use LegacyTransaction with the ZIP 143 and
ZIP 243 APIs.

zip_0143.py

@@ -3,10 +3,10 @@ from pyblake2 import blake2b
 import struct
 
 from transaction import (
+    LegacyTransaction,
     MAX_MONEY,
     OVERWINTER_TX_VERSION,
     Script,
-    Transaction,
 )
 from tv_output import render_args, render_tv, Some
 from tv_rand import Rand
@@ -111,7 +111,7 @@ def main():
 
     test_vectors = []
     for i in range(10):
-        tx = Transaction(rand, OVERWINTER_TX_VERSION)
+        tx = LegacyTransaction(rand, OVERWINTER_TX_VERSION)
         scriptCode = Script(rand)
         nIn = rand.i8() % (len(tx.vin) + 1)
         if nIn == len(tx.vin):

zip_0243.py

@@ -3,10 +3,10 @@ from pyblake2 import blake2b
 import struct
 
 from transaction import (
+    LegacyTransaction,
     MAX_MONEY,
     SAPLING_TX_VERSION,
     Script,
-    Transaction,
 )
 from tv_output import render_args, render_tv, Some
 from tv_rand import Rand
@@ -118,7 +118,7 @@ def main():
 
     test_vectors = []
     for _ in range(10):
-        tx = Transaction(rand, SAPLING_TX_VERSION)
+        tx = LegacyTransaction(rand, SAPLING_TX_VERSION)
         scriptCode = Script(rand)
         nIn = rand.i8() % (len(tx.vin) + 1)
         if nIn == len(tx.vin):

zip_0244.py

@@ -6,7 +6,7 @@ from transaction import (
     MAX_MONEY,
     NU5_TX_VERSION,
     Script,
-    Transaction,
+    TransactionV5,
 )
 from tv_output import render_args, render_tv, Some
 from tv_rand import Rand
@@ -266,7 +266,7 @@ def main():
 
     test_vectors = []
     for _ in range(10):
-        tx = Transaction(rand, NU5_TX_VERSION, consensusBranchId)
+        tx = TransactionV5(rand, consensusBranchId)
         txid = txid_digest(tx)
 
         # If there are any transparent inputs, derive a corresponding transparent sighash.