Move language and timeZone in Site to Locale

[twostraws]

Something like this: var locales: [Locale] { [.init(identifier: "en")] }

[twostraws]

I think we should push this to the next release, say in a month or two. I want to give it a try in a branch, and let multi-lingual site developers try it out to provide feedback before we commit.

[JPToroDev]

Good plan!