test: add block 2016 to mock mainnet

The next commit requires an additional mainnet block which changes the difficulty.

Also fix a few minor mistakes in the test (suite):
- rename the create_coinbase retarger_period argument to halving_period. Before bitcoin#31583 this was hardcoded for regtest where these values are the same.
- drop unused fees argument from mine helper

Finally the CPU miner instructions for generating the alternative mainnet chain are expanded.

Github-Pull: #33446
Rebased-From: 4c3c1f42cf

test/functional/test_framework/blocktools.py

@@ -144,7 +144,7 @@ def script_BIP34_coinbase_height(height):
     return CScript([CScriptNum(height)])
 
 
-def create_coinbase(height, pubkey=None, *, script_pubkey=None, extra_output_script=None, fees=0, nValue=50, retarget_period=REGTEST_RETARGET_PERIOD):
+def create_coinbase(height, pubkey=None, *, script_pubkey=None, extra_output_script=None, fees=0, nValue=50, halving_period=REGTEST_RETARGET_PERIOD):
     """Create a coinbase transaction.
 
     If pubkey is passed in, the coinbase output will be a P2PK output;
@@ -158,7 +158,7 @@ def create_coinbase(height, pubkey=None, *, script_pubkey=None, extra_output_scr
     coinbaseoutput = CTxOut()
     coinbaseoutput.nValue = nValue * COIN
     if nValue == 50:
-        halvings = int(height / retarget_period)
+        halvings = int(height / halving_period)
         coinbaseoutput.nValue >>= halvings
         coinbaseoutput.nValue += fees
     if pubkey is not None: