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GH-31506: [Python] Address docstrings in Streams and File Access (Factory Functions) (#33609)

# Which issue does this PR close?
Closes #31506

# Rationale for this change
Ensure docstrings for [Streams and File Access](https://arrow.apache.org/docs/python/api/files.html) - Factory Functions - have an Examples section:

# What changes are included in this PR?
Added docstring examples for:
- `pyarrow.input_stream`
- `pyarrow.output_stream`
- `pyarrow.memory_map`
- `pyarrow.create_memory_map` 

 Also pytest argument ` --disable-warnings` for `pytest-cython` is added, see https://github.com/lgpage/pytest-cython/issues/3: 

```python
=============================== warnings summary ===============================
opt/conda/envs/arrow/lib/python3.9/site-packages/pytest_cython/plugin.py:57
  /opt/conda/envs/arrow/lib/python3.9/site-packages/pytest_cython/plugin.py:57: PytestRemovedIn8Warning: The (fspath: py.path.local) argument to DoctestModule is deprecated. Please use the (path: pathlib.Path) argument instead.
  See https://docs.pytest.org/en/latest/deprecations.html#fspath-argument-for-node-constructors-replaced-with-pathlib-path
    return DoctestModule.from_parent(parent, fspath=path)
```

# Are these changes tested?
Yes, locally with `pytest --doctest-cython --disable-warnings pyarrow` and on the CI with `Python / AMD64 Conda Python 3.9 Sphinx & Numpydoc ` build.

# Are there any user-facing changes?
No.
* Closes: #31506

Authored-by: Alenka Frim <frim.alenka@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>