ENH: IO support for R data files with `pandas.read_rdata` and `DataFrame.to_rdata`
- [X] closes #40287
- [X] tests added / passed
- [X] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [X] whatsnew entry
- [X] install.rst entry
- [X] io.rst entry

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Note: This PR relies on a new dependency, [**`pyreadr`**](https://pypi.org/project/pyreadr/).






