return type of locale negotiation

[longlho]

cc @zbraniecki

In addition to returning an array of matched locales, I was wondering if we can actually return Intl.Locale[] instead. The benefit being that this solidify Intl.Locale as the data model representing Locale within ECMA402 and it also come already parsed with extensions builtin. Thoughts?

[lionel-rowe]

I think all current similar Intl APIs return strings:

Intl.NumberFormat.supportedLocalesOf([new Intl.Locale('es')]) // string[]
new Intl.PluralRules().resolvedOptions().locale // string

The main disadvantage of returning Intl.Locale objects is they can't be compared for equality by value.