Merge bitcoin/bitcoin#16333: test: Set BIP34Height = 2 for regtest

222290f543 test: Set BIP34Height = 2 for regtest (MarcoFalke)
fac90c55be test: Create all blocks with version 4 or higher (MarcoFalke)

Pull request description:

  BIP34 is active on the current tip of mainnet, so all miners must obey it. It would be nice if it also was active in fresh regtest instances from the earliest time possible.

  I changed the BIP34 height to `2`, so that the block at height=1 may be used to mine a duplicate coinbase. (Needed to test mainnet behaviour)

  This pull is done in two commits:

  *  test: Create all blocks with version 4 or higher:
     Now that BIP34 is activated earlier, we need to create blocks with a higher version number. Just bump it to 4 instead of 2 to avoid having to bump it again later.

  *  test: Set BIP34Height = 2 for regtest:
     This fixes the BIP34 implementation in the tests (to match the one of the Core codebase) and updates the tests where needed

ACKs for top commit:
  ajtowns:
    ACK 222290f543
  jonatack:
    ACK 222290f543 tested and reviewed rebased to current master 5e213822f8
  theStack:
    Tested ACK 222290f543

Tree-SHA512: d69c637a62a64b8e87de8c7f0b305823d8f4d115c1852514b923625dbbcf9a4854b5bb3771ff41702ebf47c4c182a4442c6d7c0b9f282c95a34b83e56a73939b

test/functional/rpc_blockchain.py

@@ -140,7 +140,7 @@ class BlockchainTest(BitcoinTestFramework):
         assert_greater_than(res['size_on_disk'], 0)
 
         assert_equal(res['softforks'], {
-            'bip34': {'type': 'buried', 'active': False, 'height': 500},
+            'bip34': {'type': 'buried', 'active': True, 'height': 2},
             'bip66': {'type': 'buried', 'active': False, 'height': 1251},
             'bip65': {'type': 'buried', 'active': False, 'height': 1351},
             'csv': {'type': 'buried', 'active': False, 'height': 432},