Fix language selector

[roryabraham]

cc @jasperhuangg

Details

There were a few issues here:

1. The preferences prop was not being provided
2. We were using Onyx.merge instead of Onyx.set (not a problem per-se but weird for a value that's just a singular string)
3. We were using Onyx.merge inline in a component callback instead of via an action.
4. The Picker component is infuriating and triggers the onChange callback multiple times.

I'm not 100% sure what was causing the crash, but _after hooking up preferredLocale via Onyx, I was getting an infinite loop where:

1. User triggers onChange to update preferred locale in Onyx
2. Onyx updates preferred locale in Picker
3. onChange is triggered again (because the preferredLocale had changed), and this would restart the loop.

Fixed Issues

Fixes #3606

Tests / QA Steps

1. Open Settings -> Preferences, and toggle the preferred locale.
2. Verify that the language of the app switches from English -> Spanish, or vice-versa.
3. Repeat the previous two steps.

Tested On

• Web
• Mobile Web
• Desktop
• iOS
• Android

Screenshots

Web

Mobile Web

Desktop

iOS

Android

[robertjchen]

Looks solid! 👍

[OSBotify]

🚀 Deployed to staging in version: 1.0.70-7🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅

[OSBotify]

🚀 Deployed to production in version: 1.0.73-3🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅