: config: add python support for configuration variable types (#2184)

Summary:


this adds python-side config support for a couple of additional rust types. specifically, it introduces `PyEncoding` to bridge string values onto `hyperactor::data::Encoding`, and `PyPortRange` to bridge python `(start, end)` tuples or `"start..end"` strings onto `Range<u16>`. both are wired into `declare_py_config_type!` so they work with `monarch.configure(...)`, and the new tests cover parsing, validation, and round-tripping for the supported formats.

Differential Revision: D89555029

Author: shayne-fletcher