test: rename CTransaction .sha256 -> .txid_int for consistency

Note that we unfortunately can't use a scripted diff here, as the same
property name is also used for `CBlockHeader`/`CBlock` instances.

test/functional/test_framework/p2p.py

@@ -911,7 +911,7 @@ class P2PDataStore(P2PInterface):
 
         with p2p_lock:
             for tx in txs:
-                self.tx_store[tx.sha256] = tx
+                self.tx_store[tx.txid_int] = tx
 
         reject_reason = [reject_reason] if reject_reason else []
         with node.assert_debug_log(expected_msgs=reject_reason):