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/test_framework/messages.py

@@ -753,14 +753,10 @@ class CBlockHeader:
         return hash256(self._serialize_header())[::-1].hex()
 
     @property
-    def sha256(self):
+    def hash_int(self):
         """Return block header hash as integer."""
         return uint256_from_str(hash256(self._serialize_header()))
 
-    # TODO: get rid of this method, replace call-sites by .sha256 access (if return value is used)
-    def rehash(self):
-        return self.sha256
-
     def __repr__(self):
         return "CBlockHeader(nVersion=%i hashPrevBlock=%064x hashMerkleRoot=%064x nTime=%s nBits=%08x nNonce=%08x)" \
             % (self.nVersion, self.hashPrevBlock, self.hashMerkleRoot,
@@ -819,7 +815,7 @@ class CBlock(CBlockHeader):
 
     def is_valid(self):
         target = uint256_from_compact(self.nBits)
-        if self.sha256 > target:
+        if self.hash_int > target:
             return False
         for tx in self.vtx:
             if not tx.is_valid():
@@ -830,7 +826,7 @@ class CBlock(CBlockHeader):
 
     def solve(self):
         target = uint256_from_compact(self.nBits)
-        while self.sha256 > target:
+        while self.hash_int > target:
             self.nNonce += 1
 
     # Calculate the block weight using witness and non-witness