feat: support preferredDatePickerStyle in iOS 14

[vonovak]

Summary

The PR was opened by @SConaway in #211, who raised the issue about weird appearance in ios 14. @vonovak took over most of the implementation. This PR was opened just to trigger automatic release (that was not handled before due to wrong format of commit message).

This adds support for preferredDatePickerStyle to the module. I took the android-only display prop and extended the support for ios too, as opposed to adding a new ios-only prop.

The implementation was quite involved; for display: spinner, compact and inline we just assign those to preferredDatePickerStyle but for default we first need to find out what that is going to be, which is determined by the OS, and hence there is a async call across the bridge to find this out. The value could be cached I suppose, but that can be done later.

I also refactored the example app so that all the possible combinations can be properly tested. That also means changing e2e tests 😅

this requires xcode 11 to build, so we'll make this a breaking change

This closes #203, closes #75

Test Plan

Build and test the example app on xcode 11 and xcode 12

What's required for testing (prerequisites)?

What are the steps to reproduce (after prerequisites)?

Compatibility

OS	Implemented
iOS	✅❌
Android	✅❌

Checklist

• I have tested this on a device and a simulator
• I added the documentation in README.md
• I mentioned this change in CHANGELOG.md
• I updated the typed files (TS and Flow)
• I added a sample use of the API in the example project (example/App.js)

[vonovak]

🎉 This PR is included in version 3.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[scarlac]

Thanks @vonovak ! Much appreciated.

FYI: A coworker had an issue where an @available rule wouldn't prevent Xcode from checking the block where we were manually setting the preferred style ourselves. He was running Xcode 11.2. It seemed to work on another machine with Xcode 11.4. Despite Apple's docs saying version Xcode >=11.0. Just in case someone reports compilation issues, try asking them to upgrade their Xcode.

[abdo17rabah]

How can i please update the package to use display= "spinner"

[SConaway]

@abdo17rabah

Assuming you're on the latest version (3.0.8 as of now), set that prop on the component you're rendering (either in a class's render() or a function's return) like this: <RNDateTimePicker display="spinner" value={date} onChange={setDate} />. Is this what you mean?