Merge bitcoin#29400: test: Fix SegwitV0SignatureMsg nLockTime signedness

fab1572 test: Fix SegwitV0SignatureMsg nLockTime signedness (MarcoFalke)

Pull request description:

  It is unsigned in Bitcoin Core, so the tests should match it:

  https://github.com/bitcoin/bitcoin/blob/5b8990a1f3c49b0b02b7383c69e95320acbda13e/src/script/interpreter.cpp#L1611

  The bug was introduced when the code was written in 330b0f3.

  (Lowercase `i` means signed, see https://docs.python.org/3/library/struct.html#format-characters)

ACKs for top commit:
  epiccurious:
    Tested ACK fab1572.
  Eunovo:
    Tested ACK bitcoin@fab1572
  achow101:
    ACK fab1572

Tree-SHA512: 68cb8582f6af22e6abb2fc9d6770277501baa0f9873e2e8d47699e87096fc5d4b9de45fa07199757b6e945c99d4c4ea95f01478322f2c093ef95cf5e0c78522b

Author: achow101

test/functional/test_framework/script.py

@@ -747,7 +747,7 @@ def SegwitV0SignatureMsg(script, txTo, inIdx, hashtype, amount):
     ss += struct.pack("<q", amount)
     ss += struct.pack("<I", txTo.vin[inIdx].nSequence)
     ss += ser_uint256(hashOutputs)
-    ss += struct.pack("<i", txTo.nLockTime)
+    ss += txTo.nLockTime.to_bytes(4, "little")
     ss += struct.pack("<I", hashtype)
     return ss