gh-88336: Fix UnicodeDecodeError with multibyte utf8 characters in ShareableList

[junnplus]

This PR fix UnicodeDecodeError with multibyte utf8 characters in ShareableList.

>> from multiprocessing.shared_memory import ShareableList
>>> strings = ["Boom 💥 💥 💥"]
>>> ShareableList(strings)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/Jun/.pyenv/versions/3.9.0/lib/python3.9/multiprocessing/shared_memory.py", line 479, in __repr__
    return f'{self.__class__.__name__}({list(self)}, name={self.shm.name!r})'
  File "/Users/Jun/.pyenv/versions/3.9.0/lib/python3.9/multiprocessing/shared_memory.py", line 435, in __getitem__
    v = back_transform(v)
  File "/Users/Jun/.pyenv/versions/3.9.0/lib/python3.9/multiprocessing/shared_memory.py", line 277, in <lambda>
    1: lambda value: value.rstrip(b'\x00').decode(_encoding),  # str
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf0 in position 15: unexpected end of data

https://bugs.python.org/issue44170

• Issue: ShareableList cannot safely handle multibyte utf-8 characters #88336

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[junnplus]

>>> from multiprocessing.shared_memory import ShareableList
>>> s1 = ShareableList(['1234567'])
>>> s1.format
'8s'
>>> s2 = ShareableList(['12345678'])
>>> s2.format
'16s'
>>> s1[0] = '12345678'  # Is this behavior expected?
>>> s1.format
'8s'
>>> s3 = ShareableList(s1)
>>> s3.format
'16s'

[github-actions]

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[github-actions]

This PR is stale because it has been open for 30 days with no activity.