proto.btc.tx.new: set sequence numbers for all inputs explicitly

Bitcoin Core v24.0.1 introduces a welcome but undocumented change in the
behavior of the ‘createrawtransaction’ RPC call: when one sequence number is
set, then the sequence numbers for the remaining inputs are automatically set
to the same value.  This occurs even when the ‘replaceable’ and ‘locktime’
arguments are not used.

To ensure this behavior across all coins and daemon versions, always set
sequence numbers for all inputs explicitly to the same value, ignoring
‘replaceable’ and ‘locktime’.

mmgen/proto/btc/tx/new.py

@@ -110,18 +110,18 @@ async def create_serialized(self,locktime=None,bump=None):
 
 		if not bump:
 			self.inputs.sort_bip69()
-			# do this only after inputs are sorted
-			if opt.rbf:
-				self.inputs[0].sequence = self.proto.max_int - 2 # handles the nLockTime case too
-			elif locktime:
-				self.inputs[0].sequence = self.proto.max_int - 1
+			# Set all sequence numbers to the same value, in conformity with the behavior of most modern wallets:
+			seqnum_val = self.proto.max_int - (2 if opt.rbf else 1 if locktime else 0)
+			for i in self.inputs:
+				i.sequence = seqnum_val
 
 		self.outputs.sort_bip69()
 
-		inputs_list = [
-			{'txid':e.txid,'vout':e.vout,'sequence':e.sequence} if n == 0 and e.sequence else
-			{'txid':e.txid,'vout':e.vout}
-				for n,e in enumerate(self.inputs) ]
+		inputs_list = [{
+				'txid':     e.txid,
+				'vout':     e.vout,
+				'sequence': e.sequence
+			} for n,e in enumerate(self.inputs) ]
 
 		outputs_dict = {e.addr:e.amt for e in self.outputs}