Support both - and _ as locale separators

[oberien]

Currently, Locale::from_str only supports dash-delimited locales like de-DE. However, often times locales are represented with an underscore like de_DE. This PR adds support for allowing both variations to be passed to Locale::from_str.

It also updates to CLDR 39.0.0 by using the json files from https://github.com/unicode-org/cldr-json/tree/39205fdc027c935e52a268afcf01cd240f3c442d/cldr-json/cldr-numbers-full/main.

All of the diff in the num-format/ directory was autogenerated by running ./scripts/locale.sh (except for removing #![deny(deprecated)] from num-format/src/lib.rs as the deprecated mem::uninitialized is used).