Merge #19328: Add gettxoutsetinfo hash_type option

40506bf93f test: Test gettxouttsetinfo hash_type option (Fabian Jahr)
f17a4d1c4d rpc: Add hash_type NONE to gettxoutsetinfo (Fabian Jahr)
a712cf6f68 rpc: gettxoutsetinfo can specify hash_type (only legacy option for now) (Fabian Jahr)
605884ef21 refactor: Extract GetBogoSize function (Fabian Jahr)

Pull request description:

  This is another intermediate part of the Coinstats Index (tracked in #18000).

  Sjors suggested [here](https://github.com/bitcoin/bitcoin/pull/18000#issuecomment-641423019) that the part of the changes in #19145 that don't rely on the new `hash_type` muhash, i.e. that are for `hash_type=none`, could be merged separately from everything involving muhash. So these changes are extracted from #19145 here and can be merged without any other requirements.

  Building the index with no UTXO set hash is still valuable because `gettxoutsetinfo` can still be used to audit the `total_amount` for example. By itself this PR is not a huge improvement, `hash_type=none` is speeding up `gettxoutsetinfo` by about 10%, but it enables the implementation of an index on top of it in a follow-up and that means large parts of the index code of Coinstats Index can be merged while reviews for the hashing algorithm might take longer.

ACKs for top commit:
  MarcoFalke:
    ACK 40506bf93f 🖨
  Sjors:
    tACK 40506bf93f

Tree-SHA512: 3964c2b8eed427511b1aa9b2ef285dff27dc4d1537d72c3911e435b6e6b40912232da4acb3a09bd19a0372ddffa44103388d8a650169d95a4a727b970d210add

test/functional/rpc_blockchain.py

@@ -241,6 +241,17 @@ class BlockchainTest(BitcoinTestFramework):
         del res['disk_size'], res3['disk_size']
         assert_equal(res, res3)
 
+        self.log.info("Test hash_type option for gettxoutsetinfo()")
+        # Adding hash_type 'hash_serialized_2', which is the default, should
+        # not change the result.
+        res4 = node.gettxoutsetinfo(hash_type='hash_serialized_2')
+        del res4['disk_size']
+        assert_equal(res, res4)
+
+        # hash_type none should not return a UTXO set hash.
+        res5 = node.gettxoutsetinfo(hash_type='none')
+        assert 'hash_serialized_2' not in res5
+
     def _test_getblockheader(self):
         node = self.nodes[0]