After Intl.NumberFormat v3, default useGrouping is "auto".
We also fix test/intl402/NumberFormat/test-option-useGrouping.js. After v3,
it accepts string and boolean.
This patch is intended to cover only one aspect of the proposal for
ECMA402: the "grouping enum" feature. It also includes coverage for the
formatting option as already defined by the latest version of ECMA402.