RFC: iOS app upload service #6893

• Windows / Linux users often encounter a situation where they have finished building their app with expo build:ios and then can't upload it to the App Store without getting access to a Mac.
• Mac users often will submit the app with an older version of Xcode on their machine and there will be a cryptic error that seems like it's our fault.
• traveling-fastlane adds a pretty hefty dependency to expo-cli, along with some unpleasant warnings on installation due to how optional dependencies work. (we still need this for build credentials)

What if we just did the equivalent expo upload:ios on the server side instead? Idea via @EvanBacon