ENH: Add I/O support of XML with pandas.read_xml and DataFrame.to_xml…
… (GH27554)

- [X] closes #27554 
- [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] io entry
- [X] install entry

To Do List
- [ ] Add `parse_dates` feature for `read_xml`.
- [ ] Add tests for `storage_options`. 
- [ ] Add tests for `ParserError`, `OSError`, `URLError`, etc. 
- [ ] Add `xpath_vars` feature to pass `$` variables in `xpath` expression. See [lxml xpath() method](https://lxml.de/xpathxslt.html#the-xpath-method).
- [ ] Add `xsl_params` feature to pass values into XSLT script. See [lxml stylesheet parameters](https://lxml.de/xpathxslt.html#stylesheet-parameters).
- [ ] Add `iterparse` feature for memory efficient parsing of large XML. See [etree iterparse](https://docs.python.org/3/library/xml.etree.elementtree.html#xml.etree.ElementTree.iterparse) and  [lxml iterparse](https://lxml.de/3.2/parsing.html#iterparse-and-iterwalk).
