memory leak observed in python 3.12.1

[TheRealMcoy]

This library appears to leak memory in Unpacker method under Python 3.12.1

reproducer script:

import msgpack
from io import BytesIO

while True:

   buf = BytesIO()
   for i in range(100):
      buf.write(msgpack.packb(i, use_bin_type=True))

   buf.seek(0)

   unpacker = msgpack.Unpacker(buf, raw=False)
   for unpacked in unpacker:
       print(unpacked)

Python 3.11.7 after 10 minute run:

Python 3.12.1 after 10 minute run: