[TIMOB-5882] iOS: Add Android Style Picker On iPhone

Titanium currently allows the option to force Android to use an iOS-style "spinner" picker. Would it be possible to also allow an option to force iOS to use an Android-style "flat" picker? An example use-case for this is when wanting a picker mechanism as part of the layout of a screen (kind of like how an HTML form has a dropdown list), or in any case where the iOS picker's size (216px/pt tall) is too large for the desired UX. Setting this override could use the existing useSpinner option (and default to true on iOS), or replace the useSpinner property with probably a more flexible "spinnerStyle" property with options like "system default", "android", and "iphone". The default would be, obviously "system default", while the other two options would provide overrides for their opposite platform (ie - setting style:"iphone" on an iPhone would simply use the default, but setting style:"android" on an iPhone would trigger the override).