test: rename CBlockHeader .rehash()/.sha256 -> .hash_int for consistency

Note that we unfortunately can't use a scripted diff here, as the
`sha256` symbol is also used for other instances (e.g. as function
in hashlib, or in the `UTXO` class in p2p_segwit.py).

test/functional/interface_zmq.py

@@ -424,7 +424,7 @@ class ZMQTest (BitcoinTestFramework):
         block.solve()
         assert_equal(self.nodes[0].submitblock(block.serialize().hex()), None)
         tip = self.nodes[0].getbestblockhash()
-        assert_equal(int(tip, 16), block.sha256)
+        assert_equal(int(tip, 16), block.hash_int)
         orig_txid_2 = self.wallet.send_self_transfer(from_node=self.nodes[0])['txid']
 
         # Flush old notifications until evicted tx original entry