Add documentation and code examples for consider-using-with (#6009)

doc/data/messages/c/consider-using-with/bad.py

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+file = open("foo.txt", "r", encoding="utf8")  # [consider-using-with]
+contents = file.read()
+file.close()

doc/data/messages/c/consider-using-with/details.rst

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+This message applies to callables of Python's stdlib which can be replaced by a ``with`` statement.
+It is suppressed in the following cases:
+
+- the call is located inside a context manager
+- the call result is returned from the enclosing function
+- the call result is used in a ``with`` statement itself

doc/data/messages/c/consider-using-with/good.py

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+with open("foo.txt", "r", encoding="utf8") as file:
+    contents = file.read()

doc/data/messages/c/consider-using-with/related.rst

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+- `PEP 343 <https://peps.python.org/pep-0343/>`_
+- `Context managers in Python <https://johnlekberg.com/blog/2020-10-11-ctx-manage.html>`_ by John Lekberg