Show "maxlen" in deque repr

[wjandrea]

collections.deque has a maxlen attribute that should be shown in its repr if defined, just like its default repr does.

This was brought up on Stack Overflow: https://stackoverflow.com/questions/71981214/python-deque-maxlen-does-not-show

Examples

Standard Python REPL:

>>> deque(range(10), maxlen=10)
deque([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], maxlen=10)

IPython:

In [2]: deque(range(10), maxlen=10)
Out[2]: deque([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

IPython after this change:

In [2]: deque(range(10), maxlen=10)
Out[2]: deque([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], maxlen=10)

And just to be sure, existing behaviour is unchanged if no maxlen is provided or the deque is recursive:

In [3]: deque(range(10))
Out[3]: deque([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

In [4]: dq = deque(range(10), maxlen=10)

In [5]: dq.append(dq)

In [6]: dq
Out[6]: deque([1, 2, 3, 4, 5, 6, 7, 8, 9, deque(...)], maxlen=10)

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P.S. LMK if this change requires adding a test or a whatsnew entry, or anything else.

[Carreau]

Thanks, that seem reasonable.