`DefaultLocale` is too coarse-grained

While I find `DefaultLocale` helpful for methods like `String::toUpperCase`, I find it's an annoyance for methods like `String::formatted` and `String::format`. (Note that the former doesn't even have an overload that takes a `Locale`.) Also, when locale-agnostic is the typical case, it's better to do `Locale.setDefault(Locale.Category.FORMAT, Locale.ROOT)` and specify an explicit `Locale` in the exceptional case.