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/p2p_fingerprint.py

@@ -79,7 +79,7 @@ class P2PFingerprintTest(BitcoinTestFramework):
 
         # Force reorg to a longer chain
         node0.send_without_ping(msg_headers(new_blocks))
-        node0.wait_for_getdata([x.sha256 for x in new_blocks])
+        node0.wait_for_getdata([x.hash_int for x in new_blocks])
         for block in new_blocks:
             node0.send_and_ping(msg_block(block))